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/FP/MipsFP.cc b/src/compiler/codegen/mips/FP/MipsFP.cc
index acbac7f..4501210 100644
--- a/src/compiler/codegen/mips/FP/MipsFP.cc
+++ b/src/compiler/codegen/mips/FP/MipsFP.cc
@@ -217,7 +217,7 @@
     loadValueAddress(cUnit, rlSrc1, r_A0);
     oatClobber(cUnit, r_A0);
     loadValueAddress(cUnit, rlSrc2, r_A1);
-    UNIMP(FATAL) << "Need callout to handler";
+    UNIMPLEMENTED(FATAL) << "Need callout to handler";
 #if 0
     genDispatchToHandler(cUnit, templateOpcode);
 #endif