Add arter97 optimizations

 - Use Linaro GCC 4.9 toolchain instead of previous Google GCC 4.7
 - Enable -O3 and replace -O2 and -Os
 - Disable -Wunused
 - Move TARGET_RELEASE_CFLAGS to TARGET_GLOBAL_CFLAGS
 - Add -fno-tree-vectorize flag
 - Add -fmodulo-sched flag
 - Add -fmodulo-sched-allow-regmoves flag
 - Add -fno-inline-functions flag
 - Add -funroll-loops flag
 - Add -mvectorize-with-neon-quad flag
 - Add -Qunused-arguments -Wno-unknown-warning-option to CLANG_CONFIG_EXTRA_CFLAGS (by JustArchi)
 - Add -O3 to CLANG_CONFIG_EXTRA_CFLAGS

Signed-off-by: Park Ju Hyung <qkrwngud825@gmail.com>