* configure.ac (LIBXML2_CFLAGS): Fix xcrun-related quoting problem.

Reported by YAMAMOTO Mitsuharu in:
http://lists.gnu.org/archive/html/emacs-devel/2013-12/msg00995.html

ChangeLog

+2013-12-29  Paul Eggert  <eggert@cs.ucla.edu>
+
+	* configure.ac (LIBXML2_CFLAGS): Fix xcrun-related quoting problem.
+	Reported by YAMAMOTO Mitsuharu in:
+	http://lists.gnu.org/archive/html/emacs-devel/2013-12/msg00995.html
+
 2013-12-28  Jan Djärv  <jan.h.d@swipnet.se>
 
 	* configure.ac: Fix CC detection for xcrun case.

configure.ac

@@ -3296,7 +3296,7 @@ if test "${with_xml2}" != "no"; then
   # Built-in libxml2 on OS X 10.8 lacks libxml-2.0.pc.
   if test "${HAVE_LIBXML2}" != "yes" -a "$opsys" = "darwin"; then
     SAVE_CPPFLAGS="$CPPFLAGS"
-    CPPFLAGS="$CPPFLAGS -I'$xcsdkdir/usr/include/libxml2'"
+    CPPFLAGS=$CPPFLAGS' -I"$xcsdkdir"/usr/include/libxml2'
     AC_CHECK_HEADER(libxml/HTMLparser.h,
       [AC_CHECK_DECL(HTML_PARSE_RECOVER, HAVE_LIBXML2=yes, ,
       		     [#include <libxml/HTMLparser.h>])])