Remove outdated comment
Add some points about having fbc parse .h files directly
Solve out "targets" variable

It's no longer needed since now all targets are always enabled.
Remove AST stats

Useless - better use something like valgrind massif to debug memory usage.
util: Remove hMakePrettyByteSize() (unused)
util: Include hashStats()/hashDump() in debug build only
cpp: Simplify #if condition expression evaluation

cpp now has its own simple cppEval() function, replacing the use of
astFold(). astFold()'s partial folding support is useless for the cpp,
since the #if condition must always be evaluated anyways - there's no point
in "folding as much as possible". cppEval() is much simpler.

cppEval() will only evaluate &&, || and ?: operands when needed, so the
old semantics of only showing "assuming undefined" warnings when it
actually matters should still work fine.
Don't fold expressions
ast: Remove astFold() & co (unused)
Remove -include option (can pass *.h files as-is instead)
Remove bad includes from non-dos.fbfrog
Remove -undef option
Remove -keepundefs option
ast: Remove ASTCLASS_PPUNDEF (unused)
Remove -appendbi option
ast: Remove ASTATTRIB_UNIQUE (unused)