bump c/c++ standard to gnu11

needed for constexpr

Marlin/Makefile

 CINCS = ${addprefix -I ,${VPATH}}
 CXXINCS = ${addprefix -I ,${VPATH}}
 
-# Compiler flag to set the C Standard level.
-# c89   - "ANSI" C
-# gnu89 - c89 plus GCC extensions
-# c99   - ISO C99 standard (not yet fully implemented)
-# gnu99 - c99 plus GCC extensions
-#CSTANDARD = -std=gnu99
+# Compiler flag to set the C/CPP Standard level.
+CSTANDARD = -std=gnu99
+CXXSTANDARD = -std=gnu++11
 CDEBUG = -g$(DEBUG)
 CWARN = -Wall -Wstrict-prototypes
 CTUNING = -funsigned-char -funsigned-bitfields -fpack-struct \
 #CEXTRA = -Wa,-adhlns=$(<:.c=.lst)
 CEXTRA = -fno-use-cxa-atexit
 
-CFLAGS := $(CDEBUG) $(CDEFS) $(CINCS) -O$(OPT) $(CWARN) $(CEXTRA) $(CTUNING)
-CXXFLAGS :=         $(CDEFS) $(CINCS) -O$(OPT) -Wall    $(CEXTRA) $(CTUNING)
+CFLAGS := $(CDEBUG) $(CDEFS) $(CINCS) -O$(OPT) $(CWARN) $(CEXTRA) $(CTUNING) $(CSTANDARD)
+CXXFLAGS :=         $(CDEFS) $(CINCS) -O$(OPT) -Wall    $(CEXTRA) $(CTUNING) $(CXXSTANDARD)
 #ASFLAGS = -Wa,-adhlns=$(<:.S=.lst),-gstabs
 LDFLAGS = -lm