Move fastboot's Mac OS code to C++.

Change-Id: I4f452860a401a115b6e8349237923949f2f476d1
diff --git a/fastboot/Android.mk b/fastboot/Android.mk
index 6443a1f..ee9f5ab 100644
--- a/fastboot/Android.mk
+++ b/fastboot/Android.mk
@@ -34,7 +34,7 @@
 endif
 
 ifeq ($(HOST_OS),darwin)
-  LOCAL_SRC_FILES += usb_osx.c util_osx.c
+  LOCAL_SRC_FILES += usb_osx.cpp util_osx.cpp
   LOCAL_LDLIBS += -lpthread -framework CoreFoundation -framework IOKit -framework Carbon
   LOCAL_CFLAGS += -Wno-unused-parameter
 endif