This creates a single M4 macro PHP_CHECK_BUILTIN and removes other
PHP_CHECK_BUILTIN_* macros. Checks are wrapped in AC_CACHE_CHECK and
PHP_HAVE_BUILTIN_* CPP macro definitions are defined to 1 if builtin
is found and undefined if not.
This also changes all PHP_HAVE_BUILTIN_ symbols to be either undefined
or defined (to value 1) and syncs all #if/ifdef/defined usages of them
in the php-src code. This way it is simpler to use them because they
don't need to be defined to value 0 on Windows, for example. This is
done as previous usages in php-src were mixed and on many places they
were only checked with ifdef.
