Move <string.h> fragment to swigfragments

Examples/test-suite/char_strings.i

@@ -11,6 +11,7 @@ below.
 
 %{
 #include <stdio.h>
+#include <string.h>
 
 #define OTHERLAND_MSG "Little message from the safe world."
 #define CPLUSPLUS_MSG "A message from the deep dark world of C++, where anything is possible."

Examples/test-suite/threads_exception.i

@@ -13,6 +13,7 @@
 %}
 
 %{
+#include <string.h>
 struct A {};
 %}
 

Examples/test-suite/varargs.i

@@ -7,6 +7,10 @@
 %varargs(int mode = 0) Foo::statictest(const char*fmt, ...);
 %varargs(2, int mode = 0) test_plenty(const char*fmt, ...);
 
+%{
+#include <string.h>
+%}
+
 %inline %{
 char *test(const char *fmt, ...) {
   return (char *) fmt;

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>
 %}