libdecnumber: Clean up includes

Clean up includes so that osdep.h is included first and headers
which it implies are not included manually.

This commit was created with scripts/clean-includes.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Eric Blake <eblake@redhat.com>
diff --git a/libdecnumber/decContext.c b/libdecnumber/decContext.c
index 68e6f60..7d97a65 100644
--- a/libdecnumber/decContext.c
+++ b/libdecnumber/decContext.c
@@ -35,8 +35,7 @@
 /* context structures.						      */
 /* ------------------------------------------------------------------ */
 
-#include <string.h>	      /* for strcmp */
-#include <stdio.h>	      /* for printf if DECCHECK */
+#include "qemu/osdep.h"
 #include "libdecnumber/dconfig.h"
 #include "libdecnumber/decContext.h"
 #include "libdecnumber/decNumberLocal.h"