Use one libc wrapper copy for sgx and other platforms (#107)

And remove bh_printf macro for other platform header files

core/shared-lib/platform/linux/bh_platform.h

@@ -77,8 +77,6 @@ typedef void* (*thread_start_routine_t)(void*);
 #define wa_free bh_free
 #define wa_strdup bh_strdup
 
-#define bh_printf printf
-
 int snprintf(char *buffer, size_t count, const char *format, ...);
 double fmod(double x, double y);
 float fmodf(float x, float y);