include stdint.h for int32_t/uint32_t

Signed-off-by: Jussi Kukkonen <jussi.kukkonen@intel.com>
Reviewed-by: Yong Bakos <ybakos@humanoriented.com>
diff --git a/libweston/compositor-headless.h b/libweston/compositor-headless.h
index 1432f70..b432b09 100644
--- a/libweston/compositor-headless.h
+++ b/libweston/compositor-headless.h
@@ -30,6 +30,8 @@
 extern "C" {
 #endif
 
+#include <stdint.h>
+
 #include "compositor.h"
 
 #define WESTON_HEADLESS_BACKEND_CONFIG_VERSION 1