[gnome-hello/wip/kill-gnome-common] build-sys: Use AX_REQUIRE_DEFINED

[David King <davidk src gnome org>]

commit 9197c59f0b33953f2a02b51b44327848fe9626e5
Author: David King <amigadave amigadave com>
Date:   Tue Jan 27 11:58:47 2015 +0000

    build-sys: Use AX_REQUIRE_DEFINED

 Makefile.am              |    3 ++-
 configure.ac             |    1 +
 m4/ax_require_defined.m4 |   37 +++++++++++++++++++++++++++++++++++++
 3 files changed, 40 insertions(+), 1 deletions(-)
---
diff --git a/Makefile.am b/Makefile.am
index aa5a13d..526df2d 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -12,7 +12,8 @@ desktop_DATA = $(desktop_in_files:.desktop.in=.desktop)
 
 EXTRA_DIST = \
        autogen.sh \
-       $(desktop_in_files)
+       $(desktop_in_files) \
+       m4/ax_require_defined.m4
 
 CLEANFILES = $(desktop_DATA)
 
diff --git a/configure.ac b/configure.ac
index 5eeb3e5..a90764b 100644
--- a/configure.ac
+++ b/configure.ac
@@ -37,6 +37,7 @@ PKG_CHECK_MODULES([GNOME_HELLO],
 # Documentation
 # *************
 
+AX_REQUIRE_DEFINED([YELP_HELP_INIT])
 YELP_HELP_INIT
 
 # ********************
diff --git a/m4/ax_require_defined.m4 b/m4/ax_require_defined.m4
new file mode 100644
index 0000000..cae1111
--- /dev/null
+++ b/m4/ax_require_defined.m4
@@ -0,0 +1,37 @@
+# ===========================================================================
+#    http://www.gnu.org/software/autoconf-archive/ax_require_defined.html
+# ===========================================================================
+#
+# SYNOPSIS
+#
+#   AX_REQUIRE_DEFINED(MACRO)
+#
+# DESCRIPTION
+#
+#   AX_REQUIRE_DEFINED is a simple helper for making sure other macros have
+#   been defined and thus are available for use.  This avoids random issues
+#   where a macro isn't expanded.  Instead the configure script emits a
+#   non-fatal:
+#
+#     ./configure: line 1673: AX_CFLAGS_WARN_ALL: command not found
+#
+#   It's like AC_REQUIRE except it doesn't expand the required macro.
+#
+#   Here's an example:
+#
+#     AX_REQUIRE_DEFINED([AX_CHECK_LINK_FLAG])
+#
+# LICENSE
+#
+#   Copyright (c) 2014 Mike Frysinger <vapier gentoo org>
+#
+#   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 1
+
+AC_DEFUN([AX_REQUIRE_DEFINED], [dnl
+  m4_ifndef([$1], [m4_fatal([macro ]$1[ is not defined; is a m4 file missing?])])
+])dnl AX_REQUIRE_DEFINED