logging: include stdarg.h for va_list
fixes tiny compile error:
CC socket.lo
In file included from socket.c:13:
../include/osmocom/core/logging.h:31: error: expected declaration
specifiers or ‘...’ before ‘va_list’
make[3]: *** [socket.lo] Error 1
diff --git a/include/osmocom/core/logging.h b/include/osmocom/core/logging.h
index fc4e2fb..72e4c93 100644
--- a/include/osmocom/core/logging.h
+++ b/include/osmocom/core/logging.h
@@ -9,6 +9,7 @@
#include <stdio.h>
#include <stdint.h>
+#include <stdarg.h>
#include <osmocom/core/linuxlist.h>
/*! \brief Maximum number of logging contexts */