Config: enable use of thread_local (with XCode 8 is out of the picture)

Author: axxel

core/src/ZXConfig.h

@@ -9,7 +9,7 @@
 // in e.g. the ReedSolomonDecoder. It is disabled by default. It can be enabled by modifying the following define.
 // Note: The Apple clang compiler until XCode 8 does not support c++11's thread_local.
 // The alternative 'static' makes the code thread unsafe.
-#define ZX_THREAD_LOCAL // '' (nothing), 'thread_local' or 'static'
+#define ZX_THREAD_LOCAL thread_local // '' (nothing), 'thread_local' or 'static'
 
 // The Galoir Field abstractions used in Reed-Solomon error correction code can use more memory to eliminate a modulo
 // operation. This improves performance but might not be the best option if RAM is scarce. The effect is a few kB big.