Replace _mesa_malloc, _mesa_calloc and _mesa_free with plain libc versions

src/mesa/drivers/dri/intel/intel_span.c

@@ -49,7 +49,7 @@ static void
 get_span_cache(struct intel_renderbuffer *irb, uint32_t offset)
 {
    if (irb->span_cache == NULL) {
-      irb->span_cache = _mesa_malloc(SPAN_CACHE_SIZE);
+      irb->span_cache = malloc(SPAN_CACHE_SIZE);
       irb->span_cache_offset = -1;
    }