svn merge svn+ssh://svn.lindenlab.com/svn/linden/release@56429 svn+ssh://svn.lindenlab.com/svn/linden/branches/maintenance@56431

This turned up the following "lost" changes:

	llapp.cpp (from maintenance r55371) - SIGPIPE fix, possibly
	llfontgl.cpp (from maintenance r50207) - whitespace only
	inventorybridge.cpp (property - non-executable)
	skins/xui/*/* (from maintenance r55380) - XML processing instruction went AWOL

corrected, removed, and updated comments throughout the code to be more useful. no code changes. SL-13762