Move <string.h> fragment to swigfragments

Lib/cdata.i

@@ -4,6 +4,8 @@
  * SWIG library file containing macros for manipulating raw C data as strings.
  * ----------------------------------------------------------------------------- */
 
+%include <swigfragments.swg>
+
 %{
 typedef struct SWIGCDATA {
     char *data;

Lib/swig.swg

@@ -442,10 +442,6 @@ namespace std {
  * Default char * and C array typemaps
  * ----------------------------------------------------------------------------- */
 
-%fragment("<string.h>", "runtime") %{
-#include <string.h>
-%}
-
 /* Set up the typemap for handling new return strings */
 
 #ifdef __cplusplus

Lib/swigfragments.swg

@@ -29,6 +29,10 @@
 #include <math.h>
 %}
 
+%fragment("<string.h>", "header") %{
+#include <string.h>
+%}
+
 %fragment("<stddef.h>", "header") %{
 #include <stddef.h>
 %}