Minor change for building on Windows

rebar.config

@@ -21,7 +21,8 @@
     {"darwin10.*-32$", "LDFLAGS", "-arch i386"},
 
     %% This will merge into basho/rebar/rebar.config eventually
-    {"win32", "CFLAGS", "/Wall /DWIN32 /D_WINDOWS /D_WIN32 /DWINDOWS"}
+    {"win32", "CFLAGS", "/Wall /DWIN32 /D_WINDOWS /D_WIN32 /DWINDOWS"},
+    {"win32", "CXXFLAGS", "-g -Wall -O3"}
 ]}.