gcc 4.4, clang 2.x and llvm-gcc are all older than the C11 requirement.
Only the icl case of BROKEN_COMPILER remains.
This also enables the existing ARMv6 decode_blockcodes() inline assembly
for Clang, whose GCC compatibility version previously excluded it.
Signed-off-by: Kacper Michajłow <kasper93@gmail.com>