ppc64 assembler issue

[David Edelsohn]

	It is the assembler that is wrong and should accept either signed
or unsigned values for lis and the others.  I noticed this strangeness in
the assembler recently myself and the handling of 32-bit values not
extended to 64-bit for some undocumented reason.  The assembler should be
fixed, not GCC.

	I also noticed that -many still imposes 32-bit versus 64-bit
instructions which also is incorrect.  PowerPC64 has a bridge-mode which
also 32-bit instructions to have some reasonable meaning, but gas does not
provide any way to allow 32-bit target instructions mixed with 64-bit
target instructions.

David