Fixing a bug which prevents builds for Windows targets.

Fixing a bug which prevents builds for Windows targets.

Without the (...) in this unlike macro, the resulting preprocessor
output is bad and generates the below compile-time error:

t/like.c: In function ‘main’:
./tap.h:70:26: error: called object is not a function or function pointer
 #define unlike           tap_skip(1, "unlike is not implemented on Windows")