Use libFirm's obst.h instead of obstack.h

[r13504]

ir/ana2/pto_init.c

@@ -35,7 +35,6 @@
 */
 
 # include <assert.h>
-# include <obstack.h>
 #ifdef HAVE_STRING_H
 # include <string.h>
 #endif
@@ -43,6 +42,7 @@
 # include <strings.h>
 #endif
 
+# include "obst.h"
 # include "pto.h"
 # include "pto_init.h"
 # include "pto_debug.h"

ir/ana2/pto_name.c

@@ -43,9 +43,9 @@
 #ifdef HAVE_STRING_H
 # include <string.h>            /* for memcpy */
 #endif
-# include <obstack.h>
 # include <errno.h>
 
+# include "obst.h"
 # include "irnode.h"
 # include "irprog.h"
 # include "xmalloc.h"