menuselect: Add libxml2 support (Patch 3)

This is the final patch in adding menuselect to Asterisk.
 - The first patch (r418832) added menuselect along with mxml
 - The second patch (r418833) removed mxml from menuselect

This patch adds support for libxml2 to menuselect, and makes libxml2 a
required library for Asterisk.

Note that the libxml2 portion of this patch was written by Sean Bright,
and was made available on a team branch:
  http://svn.digium.com/svn/menuselect/team/seanbright/libxml2/

Review: https://reviewboard.asterisk.org/r/3773/

ASTERISK-20703 #close
patches:
  some_mysterious_team_branch uploaded by seanbright (License 5060)



git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@418834 65c4cc65-6c06-0410-ace0-fbb531ad65f3

configure.ac

@@ -550,6 +550,12 @@ if test "x$JANSSON_LIB" == "x"; then
   AC_MSG_ERROR([*** JSON support not found (this typically means the libjansson development package is missing)])
 fi
 
+if test "x$PBX_LIBXML2" == "x"; then
+	AC_MSG_NOTICE(*** The Asterisk menuselect tool requires the 'libxml2' package.)
+	AC_MSG_NOTICE(*** Please install the 'libxml2' package.)
+	exit 1
+fi
+
 AST_EXT_LIB_CHECK([URIPARSER], [uriparser], [uriParseUriA], [uriparser/Uri.h])
 
 # Another mandatory item (unless it's explicitly disabled)
@@ -567,13 +573,6 @@ if test "${disable_xmldoc}" != "yes"; then
 	[#include <libxml/tree.h>
 	#include <libxml/parser.h>],
 	[LIBXML_TEST_VERSION])
-	if test "${PBX_LIBXML2}" != 1; then
-		AC_MSG_NOTICE(*** XML documentation will not be available because the 'libxml2' development package is missing.)
-		AC_MSG_NOTICE(*** Please run the 'configure' script with the '--disable-xmldoc' parameter option)
-		AC_MSG_NOTICE(*** or install the 'libxml2' development package.)
-		exit 1
-	fi
-
         AST_EXT_LIB_CHECK([LIBXSLT], [xslt], [xsltLoadStylesheetPI], [libxslt/xsltInternals.h], [${LIBXML2_LIB}], [${LIBXML2_INCLUDE}])
         AST_EXT_LIB_CHECK([LIBXSLT_CLEANUP], [xslt], [xsltCleanupGlobals], [libxslt/xsltInternals.h], [${LIBXML2_LIB}], [${LIBXML2_INCLUDE}])