Rename build system module makefiles from "lufa.MODULE.in" to "lufa_MODULE.mk" to prevent makefile from assuming the include is an old style build rule, slowing down the build process.

Prevent the BUILD module from shell-executing multiple processes to determine the avr-size flags to speed up the build, unless the size rule is invoked.

Add warnings and set warnings as errors to the SingleUSBModeTest build test makefile.

Demos/Device/ClassDriver/MassStorageKeyboard/makefile

@@ -25,12 +25,12 @@ LD_FLAGS     =
 all:
 
 # Include LUFA build script makefiles
-include $(LUFA_PATH)/Build/lufa.core.in
-include $(LUFA_PATH)/Build/lufa.sources.in
-include $(LUFA_PATH)/Build/lufa.build.in
-include $(LUFA_PATH)/Build/lufa.cppcheck.in
-include $(LUFA_PATH)/Build/lufa.doxygen.in
-include $(LUFA_PATH)/Build/lufa.dfu.in
-include $(LUFA_PATH)/Build/lufa.hid.in
-include $(LUFA_PATH)/Build/lufa.avrdude.in
-include $(LUFA_PATH)/Build/lufa.atprogram.in
+include $(LUFA_PATH)/Build/lufa_core.mk
+include $(LUFA_PATH)/Build/lufa_sources.mk
+include $(LUFA_PATH)/Build/lufa_build.mk
+include $(LUFA_PATH)/Build/lufa_cppcheck.mk
+include $(LUFA_PATH)/Build/lufa_doxygen.mk
+include $(LUFA_PATH)/Build/lufa_dfu.mk
+include $(LUFA_PATH)/Build/lufa_hid.mk
+include $(LUFA_PATH)/Build/lufa_avrdude.mk
+include $(LUFA_PATH)/Build/lufa_atprogram.mk