The Makefile gives the impression that ext2fs and msdos were excluded
(they weren't) and that you could exclude cd9660 and ufs support (you
couldn't). Allow those to be excluded.
We need to look, in the future, at trimming the number of supported
filesystems, and this will make that easier.
preference to LIBFICL{,32}. LIBFICL{,32} are now always defined, but
LDR_INTERP{,32} is defined empty when building w/o forth (aka the
simple interpreter) and defined to LIBFICL{,32} when we are building
forth.
MK_CTF, MK_SSP, MK_PROFILE, NO_PIC, and INTERNALLIB are always the
same, so set them in defs.mk. MAN= is common, so set it here too.
This removes a lot of boring repetition from the Makefiles that added
almost no value.
HELP_FILES is a loader only thing, so move it to loader.mk. Only
generate the help file if HELP_FILES is defined. Adjust Makefiles to
new convention. Fix a few cases where ${.CURDIR}/ was missing
resulting in missing bits from the help files.
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