Merge pull request #1016 from monaka/pr-reduce-string.h-20130316

Reduce string.h.

src/object.c

@@ -5,7 +5,6 @@
 */
 
 #include "mruby.h"
-#include <string.h>
 #include "mruby/string.h"
 #include "mruby/class.h"
 #include "mruby/numeric.h"

src/range.c

@@ -8,7 +8,6 @@
 #include "mruby/class.h"
 #include "mruby/range.h"
 #include "mruby/string.h"
-#include <string.h>
 
 #define RANGE_CLASS (mrb_class_obj_get(mrb, "Range"))
 

src/state.c

@@ -7,7 +7,6 @@
 #include "mruby.h"
 #include "mruby/irep.h"
 #include "mruby/variable.h"
-#include <string.h>
 
 void mrb_init_heap(mrb_state*);
 void mrb_init_core(mrb_state*);