Handle instruction and prefix identifiers properly when used in other

Handle instruction and prefix identifiers properly when used in other
places in GAS input.  Do this by adding a tokenizer state that turns off
insn and prefix generation when inside an instruction or directive, AND
adding a special case for labels.

* gas-parser.h (state): Add INSTDIR.
* gas-token.re: Switch state back to INITIAL on ';' or newline; set state
when entering instruction or directive, add special case for labels.
* gas-bison.y: Remove non-working attempt at translating INSN and PREFIX
into string token; add special case for LABEL identifiers (generated from
special case for labels in tokenizer).

svn path=/trunk/yasm/; revision=1309