Renaming HTTP_HEADER_* into HTTP_IN_HEADER_* and HTTP_OUT_HEADER_* to make it more clear which header strings should be used for incoming vs outgoing situations.
Using constants for commonly used llhttpnode context strings.

merged all changes, post copy, from the following branches:
linden/brachnes/enable-o-v
user/cg/qar-1538
user/mani/viewer2-enable-o-v

Result of svn merge -r107256:107258 svn+ssh://svn/svn/user/phoenix/license_2009_merge into trunk. QAR-1165

Result of svn merge -r71162:71205 svn+ssh://svn/svn/linden/branches/new-license into release. only changes files which are not deployed or the comments section of code.