Added '_' checking that warns of the use of "_" or "\_" in the wrong places

Added '_' checking that warns of the use of "_" or "\_" in the wrong places
Added syntax checking for common documenting problems that tex2rtf does not handle properly (like \begin{verbatim} and others needing to be on a line by themselves)
Syntax checking and curley brace matching can be turned on via the commandline, or the new OPTIONS menu choice if using a GUI.  Both are OFF by default to match current behavior
Compilation again possible now if wxUSE_DEBUG_CONTEXT is set to 0 in setup.h
Various GUI glitches fixed

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@10309 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775