This broke tests all over the place.

This reverts commit 1aa62ceb.

for compatibility with Python llbase.llsd.parse().

The Python parse() currently requires uppercase hex digits for b16"hex"
coding; lowercase hex digits cause it to raise LLSDParseError.

LLSDNotationFormatter (also LLSDNotationStreamer that uses it, plus
operator<<(std::ostream&, const LLSD&) that uses LLSDNotationStreamer) is most
useful for displaying LLSD to a human, e.g. for logging. Having the default
dump raw binary bytes into the log file is not only suboptimal, it can
truncate the output if one of those bytes is '\0'. (This is a problem with the
logging subsystem, but that's a story for another day.)

Use OPTIONS_PRETTY_BINARY wherever there is a default LLSDFormatter
::EFormatterOptions argument.

Also, allow setting LLSDFormatter subclass boolalpha(), realFormat() and
format(options) using optional constructor arguments. Naturally, each subclass
that supports this must accept and forward these constructor arguments to its
LLSDFormatter base class constructor.

Fix a couple bugs in LLSDNotationFormatter::format_impl() for an LLSD::Binary
value with OPTIONS_PRETTY_BINARY:
- The code unconditionally emitted a b(len) type prefix followed by either raw
  binary or hex, depending on the option flag. OPTIONS_PRETTY_BINARY caused it
  to emit "0x" before the hex representation of the data. This is wrong in
  that it can't be read back by either the C++ or the Python LLSD parser.
  Correct OPTIONS_PRETTY_BINARY formatting consists of b16"hex digits" rather
  than b(len)"raw bytes".
- Although the code did set hex mode, it didn't set either the field width or
  the fill character, so that a byte value less than 16 would emit a single
  digit rather than two.

Instead of having one LLSDFormatter::format() method with an optional options
argument, declare two overloads. The format() overload without options passes
the mOptions data member to the overload accepting options.

Refactor the LLSDFormatter family, hoisting the recursive format_impl() method
(accepting level) to a pure virtual method at LLSDFormatter base-class level.
Most subclasses therefore need not override either base-class format() method,
only format_impl(). In fact the short format() overload isn't even virtual.

Consistently use LLSDFormatter::EFormatterOptions enum as the options
parameter wherever such options are accepted.

replace llinfos, lldebugs, etc with new LL_INFOS(), LL_DEBUGS(), etc.

Large changes to the LLCurl::Responder API, as well as pulling in some changes to common libraries from the server codebase:

* Additional error checking in http handlers.
* Uniform log spam for http errors.
* Switch to using constants for http heads and status codes.
* Fixed bugs in incorrectly checking if parsing LLSD xml resulted in an error.
* Reduced spam regarding LLSD parsing errors in the default completedRaw http handler.  It should not longer be necessary to short-circuit completedRaw to avoid spam.
* Ported over a few bug fixes from the server code.
* Switch mode http status codes to use S32 instead of U32.
* Ported LLSD::asStringRef from server code; avoids copying strings all over the place.
* Ported server change to LLSD::asBinary; this always returns a reference now instead of copying the entire binary blob.
* Ported server pretty notation format (and pretty binary format) to llsd serialization.

* The new LLCurl::Responder API no longer has two error handlers to choose from.  Overriding the following methods have been deprecated:
** error - use httpFailure
** errorWithContent - use httpFailure
** result - use httpSuccess
** completed - use httpCompleted
** completedHeader - no longer necessary; call getResponseHeaders() from a completion method to obtain these headers.

* In order to 'catch' a completed http request, override one of these methods:
** httpSuccess - Called for any 2xx status code.
** httpFailure - Called for any non-2xx status code.
** httpComplete - Called for all status codes.  Default implementation is to call either httpSuccess or httpFailure.
* It is recommended to keep these methods protected/private in order to avoid triggering of these methods without using a 'push' method (see below).

* Uniform error handling should followed whenever possible by calling a variant of this during httpFailure:
** llwarns << dumpResponse() << llendl;
* Be sure to include LOG_CLASS(your_class_name) in your class in order for the log entry to give more context.

* In order to 'push' a result into the responder, you should no longer call error, errorWithContent, result, or completed.
* Nor should you directly call httpSuccess/Failure/Completed (unless passing a message up to a parent class).
* Instead, you can set the internal content of a responder and trigger a corresponding method using the following methods:
** successResult - Sets results and calls httpSuccess
** failureResult - Sets results and calls httpFailure
** completedResult - Sets results and calls httpCompleted

* To obtain information about a the response from a reponder method, use the following getters:
** getStatus - HTTP status code
** getReason - Reason string
** getContent - Content (Parsed body LLSD)
** getResponseHeaders - Response Headers (LLSD map)
** getHTTPMethod - HTTP method of the request
** getURL - URL of the request

* It is still possible to override completeRaw if you want to manipulate data directly out of LLPumpIO.

* See indra/llmessage/llcurl.h for more information.