Check for Text::Diff in configure script.

TODO

diff --git a/TODO b/TODO
index 9bfef9b..64b281f 100644
--- a/TODO
+++ b/TODO
@@ -29,7 +29,6 @@
 * function to copy file from one archive to another
 * do not compress if storing is smaller
 * set O_CLOEXEC flag after fopen and mkstemp
-* check for Text::Diff in configure script
 
 ! W test extra fields api
   . set

configure.ac

diff --git a/configure.ac b/configure.ac
index a2b9749..c3e5f4a 100644
--- a/configure.ac
+++ b/configure.ac
@@ -110,6 +110,8 @@
 
 gl_VISIBILITY
 
+AX_PERL_MODULE_VERSION([Text::Diff 1.41], , AC_MSG_ERROR([The Text::Diff perl module is needed by the test framework. Please install it.]))
+
 AC_CONFIG_FILES([Makefile
 		 libzip.pc
 		 libzip-uninstalled.pc

m4/ax_perl_module_version.m4

diff --git a/m4/ax_perl_module_version.m4 b/m4/ax_perl_module_version.m4
new file mode 100644
index 0000000..356e695
--- /dev/null
+++ b/m4/ax_perl_module_version.m4
@@ -0,0 +1,85 @@
+# ===========================================================================
+#  http://www.gnu.org/software/autoconf-archive/ax_perl_module_version.html
+# ===========================================================================
+#
+# SYNOPSIS
+#
+#   AX_PERL_MODULE_VERSION([MODULE VERSION], [ACTION-IF-TRUE], [ACTION-IF-FALSE])
+#
+# DESCRIPTION
+#
+#   Checks to see if the list of 'Module Version' are avaiable in the
+#   system. If all the modules in the list are avaiable ACTION-IF-TRUE is
+#   executed. Case one module is not avaiable ACTION-IF-FALSE is executed
+#   and the macro execution is aborted. NOTE: Perl is needed.
+#
+#   Example:
+#
+#     AX_PERL_MODULE_VERSION(CGI::Test 0.104 CGI::Ajax 0.694, ,
+#        AC_MSG_ERROR(Need some Perl modules))
+#
+# LICENSE
+#
+#   Copyright (c) 2009 Marco Gomes <mpglesi@gmail.com>
+#   Copyright (c) 2009 Ruben Fonseca <fonseka@gmail.com>
+#
+#   Copying and distribution of this file, with or without modification, are
+#   permitted in any medium without royalty provided the copyright notice
+#   and this notice are preserved. This file is offered as-is, without any
+#   warranty.
+
+#serial 5
+
+AU_ALIAS([AC_PERL_MODULE_VERSION], [AX_PERL_MODULE_VERSION])
+AC_DEFUN([AX_PERL_MODULE_VERSION],[dnl
+ac_perl_list_modules="$1"
+# Make sure we have perl
+if test -z "$PERL"; then
+AC_CHECK_PROG(PERL,perl,perl)
+fi
+
+# Check the number of arguments
+#args_num=`echo $ac_perl_list_modules | wc -w`
+#let "ckeck_args = $args_num % 2"
+#if test "$check_args" = "1" ; then
+#  AC_MSG_ERROR(syntax error)
+#else
+  eval
+#fi
+
+if test "x$PERL" != x; then
+  ac_failed=0
+  while test ${#ac_perl_list_modules} -gt 2 ; do
+	module_name=`echo $ac_perl_list_modules | cut -d " " -f 1`
+	module_version=`echo $ac_perl_list_modules | cut -d " " -f 2`
+	ac_perl_list_modules=`echo $ac_perl_list_modules | cut -d " " -f 3-`
+	AC_MSG_CHECKING(for perl module $module_name version $module_version)
+
+	$PERL "-M$module_name" -e exit > /dev/null 2>&1
+	if test $? -ne 0; then
+	  AC_MSG_RESULT(no);
+	  ac_failed=1
+	  ac_perl_list_modules=""
+	else
+	  version=`$PERL "-M$module_name" -e 'print $'"$module_name::VERSION" 2>&1`
+	  $PERL -e 'exit(shift cmp shift)' "$version" "$module_version"
+	  if test $? -eq 0 -o $? -eq 1 ; then
+	    AC_MSG_RESULT(ok);
+	  else
+	    AC_MSG_RESULT(no)
+	    ac_failed=1
+	    ac_perl_list_modules=""
+	  fi
+	fi;
+  done
+
+  if test "$ac_failed" = 0; then
+    :
+    $2
+  else
+    :
+    $3
+  fi
+else
+  AC_MSG_ERROR(could not find perl)
+fi])dnl