PowerPC disassembly of odd sized sections

PowerPC disassembly of odd sized sections

We shouldn't really decode a 2-byte left-over at the end of a section
as if the section contains two more bytes of zeros.  Not that it
matters very much, but this patch tidies the corner case.

	* ppc-dis.c (print_insn_powerpc): Only clear needed bytes of
	partially filled buffer.  Prevent lookup of 4-byte insns when
	only VLE 2-byte insns are possible due to section size.  Print
	".word" rather than ".long" for 2-byte leftovers.