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/sdb/symbol.cc

@@ -57,7 +57,8 @@ FunctionSymbol::FunctionSymbol() :
     Symbol(Function),
     start_address(0), end_address(0),
     type(Unknown), flags(0),
-    kernel_export(0), ee(0) {
+    kernel_export(0), ee(0),
+    impl_value(NULL) {
 }
 
 FunctionSymbol::~FunctionSymbol() {