Assemble linux32_locore.s and ia32_sigtramp.S with clang integrated assembler.
Support for .code32 and .code64 in llvm was implemented more than 2 years ago.

Tested by:      Dan McGregor <dan.mcgregor at usask dot ca>
Remove duplicate dev.xbd.*.max_requests sysctl added in r252260.

Approved by:	gibbs