Remove #if 0 and #if 1...#else guarded code

(This is what version control history is for.)

Where appropriate, turn the code into comments, commented code, or
commented debugging lines.
Fix compiler warnings with trivial fixes.

Fixes include removing dead code and variables, ifdeffing
platform-specific code, and unifdeffing non-platform-specific code.
sfundo.c: fix typos in findterm (thanks, GCC!)
sfundo.c: fix another typo in findterm (again, thanks GCC!)
Make getTempDir return a const char *, to avoid a compiler warning

No changes needed in callers, they weren't trying to mutate the string
anyway.
charview.c: remove dead code, fix more compiler warnings
gxdraw.c: fix typo in static array name
dumppfa.c: remove commented-out function that was already moved elsewhere
fontview.c: remove commented-out code
Remove support for VMS and for systems lacking snprintf

VMS is long gone; but if there are still developers for it, let's
solve portability problems at the top level, not with code buried in
the app. gnulib should help.

Similarly, snprintf is standard since C99. If we still build for
libc's that lack it, there's always gnulib.
Since we already assume C99, remove checks for C99 features
Collab code: remove more dead code and fix compiler warnings when building without collab
Fix a typo in function names, and remove more dead code
parsettf.c: remove workaround for old GCC bug
fontview.c: remove lurking support for systems without snprintf
Replace 'forever' macro with 'for (;;)': let's not make up new syntax.
wordlistparser.c: fix printf format warning
pythonui.c: fix a compiler warning for unused code in non-collab build
Remove custom allocator functions and debugging tools.

The libc allocator is likely to be better these days, as are the
built-in debugging tools. We lower the noise by removing our names.
gutils/fsys.c: fix a couple of typos in strings and comments