De-cruft the libbcc compiler infrastructure.

This patch removes the RSCompiler subclass of Compiler and moves most of its
functionality over to the original Compiler class.  Methods and variables are
re-named to make the code clearer.  In addition, unused functions have been
removed.

Change-Id: I121463df6309c377496cebea8cbb82bb49624ed1
diff --git a/tools/bcc/Main.cpp b/tools/bcc/Main.cpp
index 6b9b13d..9c6ed45 100644
--- a/tools/bcc/Main.cpp
+++ b/tools/bcc/Main.cpp
@@ -116,7 +116,7 @@
 
 static inline
 bool ConfigCompiler(RSCompilerDriver &pRSCD) {
-  RSCompiler *RSC = pRSCD.getCompiler();
+  Compiler *RSC = pRSCD.getCompiler();
   CompilerConfig *config = nullptr;
 
   config = new (std::nothrow) CompilerConfig(OptTargetTriple);