[PATCH V4] configure.ac: Fallback to older detection code if pkg-config can't find expat

[Bill Spitzak]

This paritally reverts commit a4afd90f9f0c27ed5f3f313b915c260673f8be34.

On older expat versions (ie the one on Ubuntu 12.04) there is no pkg-config
file, so fall back to a test for the header and library. In addition the
source for expat does not seem to be in a git repository but in cvs instead
and it seems preferrable to not require cvs to build wayland.

The restored test has been updated to use AC_SEARCH_LIBS. This version
uses empty square brackets for the unused branches, similar to many other
if statements in configure.ac.
---
 configure.ac |   11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/configure.ac b/configure.ac
index 0426b53..5a8e915 100644
--- a/configure.ac
+++ b/configure.ac
@@ -85,7 +85,16 @@ AC_ARG_WITH(icondir, [  --with-icondir=<dir>    Look for cursor icons here],
 AC_SUBST([ICONDIR])
 
 if test "x$enable_scanner" = "xyes"; then
-	PKG_CHECK_MODULES(EXPAT, [expat])
+	PKG_CHECK_MODULES(EXPAT, [expat], [],
+		[AC_CHECK_HEADERS(expat.h, [],
+			[AC_MSG_ERROR([Can't find expat.h. Please install expat.])])
+		 SAVE_LIBS="$LIBS"
+		 AC_SEARCH_LIBS(XML_ParserCreate, expat, [],
+			[AC_MSG_ERROR([Can't find expat library. Please install expat.])])
+		 EXPAT_LIBS="$LIBS"
+		 LIBS="$SAVE_LIBS"
+		 AC_SUBST(EXPAT_LIBS)
+		])
 fi
 
 AC_PATH_PROG(XSLTPROC, xsltproc)
-- 
1.7.9.5