Merge master v6.4.6 into DRTVWR-497 (VS2017)

SL-13416 eliminate sun/moon specular on shadowed surfaces. Cherry-picked from DRTVWR-510.

following promotion of DRTVWR-476

SL-13163 pull shader changes into DRTVWR-497

SL-12261 Remove redrawing of sky twice and timer causing it not to be re-drawn twice 2% of the time

Approved-by: Dave Houlton

Pull MAINT fixes for SL-13397 and SL-13443 into LMR#4 branch

Approved-by: Andrey Kleshchev
Approved-by: Michael Pohoreski

Eliminates stall from saveObjectCache() on region deletion

Ever since February 2010, the body of the login coroutine function has been
enclosed in try/catch (...), with an llerrs message to try to crash more
informatively than the runtime's unhandled-exception termination. Over the
years this evolved to LL_ERRS and then to CRASH_ON_UNHANDLED_EXCEPTION.

This persisted despite the August 2016 addition of generic catch clauses in
the LLCoros::toplevel() function to serve the same purpose, and despite the
subsequent introduction of the LLCoros::Stop family of exceptions to
deliberately throw into waiting coroutines on viewer shutdown.

That's exactly what was happening. When the user closed the viewer while
waiting for the response from login.cgi, the waiting operation threw
LLCoros::Stopping, which was caught by that CRASH_ON_UNHANDLED_EXCEPTION,
which crashed the viewer with LL_ERRS rather than propagating up to the
toplevel() and cleanly terminating the coroutine.

Change CRASH_ON_UNHANDLED_EXCEPTION() to LOG_UNHANDLED_EXCEPTION() and
re-throw so toplevel() can handle.

SL-13539 Fix a white artifact over the water at certain angles

Approved-by: Dave Houlton

SL-12978

Approved-by: Dave Houlton

SL-13540: Do not fail if binary bucket is too large, attempt to extract the asset type from the old style bucket. Notification still not shown.

SL-13540: Do not fail if binary bucket is too large, attempt to extract the asset type from the old style bucket. Notification still not shown.

The llappviewerwin32.cpp create_console() function called by
LLAppViewerWin32::initConsole() used to assign *stderr = *(new FILE* value),
and so forth for stdout and stdin. That dubious tactic no longer works with
the new Windows CRT introduced with VS 2015. freopen_s() works much better.

(cherry picked from commit 0b61150e)

There are separate stanzas in llappviewerwin32.cpp's create_console() function
for each of STD_INPUT_HANDLE, STD_OUTPUT_HANDLE and STD_ERROR_HANDLE. SL-13361
wants to add more code to each. Factor out new local set_stream() function and
make create_console() call it three times.

(cherry picked from commit 13b78a0c)