Stop using old gnu++0x, switch to gnu++11

Signed-off-by: falkTX <falktx@falktx.com>

source/Makefile.mk

@@ -90,7 +90,7 @@ endif
 ARM32_FLAGS = -mcpu=cortex-a7 -mtune=cortex-a7 -mfpu=neon-vfpv4 -mfloat-abi=hard -mvectorize-with-neon-quad
 
 BUILD_C_FLAGS   = $(BASE_FLAGS) -std=gnu99 $(CFLAGS)
-BUILD_CXX_FLAGS = $(BASE_FLAGS) -std=gnu++0x $(CXXFLAGS)
+BUILD_CXX_FLAGS = $(BASE_FLAGS) -std=gnu++11 $(CXXFLAGS)
 LINK_FLAGS      = $(LINK_OPTS) $(LDFLAGS)
 
 ifneq ($(MACOS),true)