this fixes a lot of previous hacks
first off, rgbds requires that labels from includes be marked as globals.
instead, 3626ddeb stuffed includes into the parent file in the preprocessor.
this meant one huge file got preprocessed every time, adding an additional
ten seconds to compile time.
running the preprocessor once for each file would create too much overhead,
so a list is fed into prequeue.py, which then makes calls to preprocessor.py.
this paves the way for compiling source files separately some day.
next, compiling previously required `make clean` to be executed first.
f3340de6 touched main.asm to force a fresh compile instead. this behavior
has been reverted. now, `make all` will only attempt to recompile if a
source file has changed.
preprocessor.py has some marginal changes. prequeue.py is created to keep
the original functionality of preprocessor.py intact. so many files are
preprocessed on first compile (1951 as of this commit) that the prequeue
call has been hidden.
compile time is reduced to 15-30 seconds on first compile, and 5-10 seconds
subsequently. the majority of this time is spent in rgbasm.
The preprocessor only runs against stdin when __main__ is activated,
instead of always running on stdin. This allows the file to be included
in an interactive python session or in other scenarios.
The include macro is now checked against only the beginning of the line,
and comments in the asm file can say "INCLUDE \"" if they need to. In
addition, the preprocessor now supports INCLUDE lines that are preceded
by a tab character. However, if this included file has multiple lines,
the output will not be automatically aligned with the initial tab. This
might cause problems with rgbasm.
