Multi-target Codegen cleanup

Trying to get a bit more consistent in the abstraction layer
naming:

     genXXX   -> high-level codegen, for ex: genIGet()
     opXXX    -> instruction-level output, for ex: opRegImm()

Also more fleshing out of the Mips codegen support.

Change-Id: Iafdf397cbb5015bfe3aa2c38680d96c7c05f8bc4
diff --git a/src/compiler/codegen/mips/ArchFactory.cc b/src/compiler/codegen/mips/ArchFactory.cc
index 2cb0731..aaaa50f 100644
--- a/src/compiler/codegen/mips/ArchFactory.cc
+++ b/src/compiler/codegen/mips/ArchFactory.cc
@@ -109,7 +109,7 @@
                     cUnit->frameSize - (spillCount * 4));
         genRegRegCheck(cUnit, kCondCc, newSP, checkReg, NULL,
                        kThrowStackOverflow);
-        genRegCopy(cUnit, rSP, newSP);         // Establish stack
+        opRegCopy(cUnit, rSP, newSP);         // Establish stack
     } else {
         opRegImm(cUnit, kOpSub, rSP,
                  cUnit->frameSize - (spillCount * 4));