core: Warn if GPU_MAX_ALLOC_PERCENT or GPU_USE_SYNC_OBJECTS is not set

...through export (Linux) or setx (Windows).

cgminer.c

@@ -7713,6 +7713,13 @@ int main(int argc, char *argv[])
 #endif
 	}
 
+#ifdef USE_SCRYPT // I don't really know if this is relevant for other mining platforms
+	if (!getenv("GPU_MAX_ALLOC_PERCENT"))
+		applog(LOG_WARNING, "WARNING: GPU_MAX_ALLOC_PERCENT is not specified!");
+	if (!getenv("GPU_USE_SYNC_OBJECTS"))
+		applog(LOG_WARNING, "WARNING: GPU_USE_SYNC_OBJECTS is not specified!");
+#endif
+
 	if (!total_pools) {
 		applog(LOG_WARNING, "Need to specify at least one pool server.");
 #ifdef HAVE_CURSES