Added benchmark skeleton, and at least stubs for all of the necessary functions

src/compile.c

@@ -0,0 +1,15 @@
+// This file contains functions related to managing multiple parse backends
+#include "hammer.h"
+#include "internal.h"
+
+static HParserBackendVTable *backends[PB_MAX] = {
+  &h__packrat_backend_vtable,
+};
+
+int h_compile(HParser* parser, HParserBackend backend, const void* params) {
+  return h_compile__m(&system_allocator, parser, backend, params);
+}
+
+int h_compile__m(HAllocator* mm__, HParser* parser, HParserBackend backend, const void* params) {
+  return backends[backend]->compile(mm__, parser, params);
+}