suppress .tx handling in Makefile

there are too many .tx files for the commands to be meaningful

better to just look at the makefile to see what's going on
no need to use python if baserom.gbc doesn't exist

this part is only reached if baserom.gbc doesn't exist,
so it's pointless to check if it does
Merge branch 'master' into rgbasm-objects
Merge branch 'master' into rgbasm-objects
preprocess everything

it makes more sense this way
move gbhw.asm and hram.asm to constants.asm

they're constants, so they have no business in pokecrystal.asm
rewrite Makefile to handle multiple rgbasm objects

for now, any new files to preprocess will trigger the targets for all objects.
this isn't a problem yet since there's still only one object.
change old .tx includes to .asm

these were forgotten about with the last preprocessor change.
this is required for object dependencies to be handled by make.
scan source files for Makefile dependencies

preprocessing should work with multiple object files now
rename make variables for graphics files
rename lzs make target to gfx
abstract make targets are now phony
use a docstring instead of comments in scan_includes
Merge pull request #202 from yenatch/rgbasm-objects

makefile: support multiple rgbasm objects