[dlg] Fix compiler warnings.

* src/dlg/dlgwrap.c: Duplicate some feature test macros from
`dlg.c`, which must come first before loading standard headers.  For
example, `freetype.h` loads `stdio.h` if compiled in debug mode.

ChangeLog

@@ -1,3 +1,11 @@
+2020-12-01  Werner Lemberg  <wl@gnu.org>
+
+	[dlg] Fix compiler warnings.
+
+	* src/dlg/dlgwrap.c: Duplicate some feature test macros from
+	`dlg.c`, which must come first before loading standard headers.  For
+	example, `freetype.h` loads `stdio.h` if compiled in debug mode.
+
 2020-12-01  Werner Lemberg  <wl@gnu.org>
 
 	* src/type42/t42parse.c: Fix `-Wformat` warnings.

src/dlg/dlgwrap.c

@@ -16,6 +16,11 @@
  */
 
 
+  /* We have to duplicate these feature test macros from `dlg.c` */
+  /* since `freetype.h` loads some affected standard headers.    */
+#define _XOPEN_SOURCE
+#define _POSIX_C_SOURCE 200809L
+
 #include <freetype/freetype.h>