These are a collection of small speed patches. They do make the
compiler faster, but not by a significant amount; they're mostly
cleanups to make understanding certain behaviour easier.
The two 'make X a string' changes combine to reduce the size of the
identifier hash table by about 1% on my testcase. I'll next see what
happens if you remove all the GIMPLE temporary variables from the
table.
Bootstrapped & tested on powerpc-darwin, except that libjava didn't
build because the Makefile wanted VMFile.java and I don't have one.