Drop zend_long64 in favor of int64_t

Also drop ZEND_HAVE_LONG64, because we already require the
presence of a int64_t type.
Fix format strings in zend_alloc
Use intptr_t for zend_intptr_t typedef

Current code doesn't work for 64bit zend_long with 32bit pointers.

If intptr_t isn't defined on some platform, we should add it to
our php_stdint.h header.
Fix allocator for 64bit zend_long with 32bit long