Don't compile libqb.cpp as Objective-C on Mac OS

With the recent changes to libqb.cpp to pull out some of the GLUT logic,
the only actual Objective-C in libqb.cpp was pulled out. That being the
case, it's no longer necessary to have libqb.mm for compiling libqb.cpp,
so we're removing it to simplify the compliation logic a bit.

Makefile

@@ -401,13 +401,8 @@ endif
 
 QBLIB := $(PATH_INTERNAL_C)/$(QBLIB_NAME).o
 
-ifneq ($(OS),osx)
 $(QBLIB): $(PATH_INTERNAL_C)/libqb.cpp
 	$(CXX) $(CXXFLAGS) $< -c -o $@
-else
-$(QBLIB): $(PATH_INTERNAL_C)/libqb.mm
-	$(CXX) $(CXXFLAGS) $< -c -o $@
-endif
 
 ifeq ($(OS),win)
 CLEAN_LIST += $(ICON_OBJ)

internal/c/libqb.cpp

@@ -13,13 +13,7 @@
 #ifdef QB64_MACOSX
 #    include <ApplicationServices/ApplicationServices.h>
 
-#    include "Cocoa/Cocoa.h"
-#    include <CoreFoundation/CoreFoundation.h>
-#    include <objc/objc-runtime.h>
-#    include <objc/objc.h>
-
 #    include <mach-o/dyld.h> //required for _NSGetExecutablePath
-
 #endif
 
 #include "mutex.h"

internal/c/libqb.mm

@@ -1,2 +0,0 @@
-#include "libqb.cpp"
-