MFC r329345: Eliminate bsd.stand.mk and -fPIC 32-bit intel builds

OK. We don't really need a bsd.stand.mk, and it was causing a -fPIC
for the toolchain to be added (bogusly) when building on amd64. Pull
all relevant defs back into defs.mk and delete bsd.stand.mk.

This saves about 15-20k on i386 loader and zfsloader which when
combined with Lua give us a lot more stack space in those constrained
environments.