g_str_equal: Provide macro for optimization
g_str_equal() is a nicer API than strcmp()==0, and less error prone.
However, forcing a function call prevents compiler from doing
optimizations. In the case it is not used as callback to GHashTable,
provide a macro that calls strcmp directly. This also has the side
effect that it forces arguments to be const char *
instead of
gconstpointer
in the case it is not used as callback, which adds type
safety.
Fixes: #2775 (closed)