Add -std=gnu11 to compiler.c.flags in platform.txt

Related to issue arduino#221

Author: eriknyquist

platform.txt

@@ -14,7 +14,7 @@ compiler.prefix=arc-elf32
 
 compiler.path={runtime.tools.arc-elf32.path}/bin/
 compiler.c.cmd=arc-elf32-gcc
-compiler.c.flags=-c -mcpu=quarkse_em -mlittle-endian -g -Os -Wall -fno-reorder-functions -fno-asynchronous-unwind-tables -fno-omit-frame-pointer -fno-defer-pop -Wno-unused-but-set-variable -Wno-main -ffreestanding -fno-stack-protector -mno-sdata -ffunction-sections -fdata-sections -fsigned-char -MMD -D__ARDUINO_ARC__
+compiler.c.flags=-c -std=gnu11 -mcpu=quarkse_em -mlittle-endian -g -Os -Wall -fno-reorder-functions -fno-asynchronous-unwind-tables -fno-omit-frame-pointer -fno-defer-pop -Wno-unused-but-set-variable -Wno-main -ffreestanding -fno-stack-protector -mno-sdata -ffunction-sections -fdata-sections -fsigned-char -MMD -D__ARDUINO_ARC__
 compiler.c.elf.cmd=arc-elf32-gcc
 compiler.c.elf.flags=-nostartfiles -nodefaultlibs -nostdlib -static -Wl,-X -Wl,-N -Wl,-mcpu=quarkse_em -Wl,-marcelf -Wl,--gc-sections
 compiler.S.flags=-c -g -x assembler-with-cpp