Many components under stand/ had CLANG_NO_IAS added when Clang's
Integrated Assembler (IAS) did not handle .codeNN directives. Clang
gained support quite some time ago, and we can now build stand/ with
IAS.
Note that in some cases there are small differences in the generated
output, so CLANG_NO_IAS should be removed only after testing (or after
finding no differences in the output).
PR: 205250, 233094
Sponsored by: The FreeBSD Foundation
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.
