Initial libjit skeleton.

Not currently generating instructions, but most of the flow is right up to
that point. A lot of work required to refactor the emitter, but wanted to
get this checked in.

src/xenia/cpu/ppc/instr_tables.h

@@ -21,7 +21,7 @@ namespace tables {
 
 static InstrType* instr_table_prep(
     InstrType* unprep, int unprep_count, int a, int b) {
-  int prep_count = pow(2.0, b - a + 1);
+  int prep_count = (int)pow(2, b - a + 1);
   InstrType* prep = (InstrType*)xe_calloc(prep_count * sizeof(InstrType));
   for (int n = 0; n < unprep_count; n++) {
     int ordinal = XESELECTBITS(unprep[n].opcode, a, b);