[PATCH V2] 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 the previous test for the header file when it fails.
Test is slightly cleaned up from previous one.

I could not use AC_SEARCH_LIBS as was suggested, as this leaves the switch
in LIBS, not EXPAT_LIBS, and thus does not match the pkg-config results.
---
 configure.ac |    7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/configure.ac b/configure.ac
index 0426b53..fc5ea55 100644
--- a/configure.ac
+++ b/configure.ac
@@ -85,7 +85,12 @@ 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.])])
+		AC_CHECK_LIB(expat, XML_ParserCreate, [EXPAT_LIBS="-lexpat"],
+			[AC_MSG_ERROR([Can't find expat library. Please install expat.])])
+		])
 fi
 
 AC_PATH_PROG(XSLTPROC, xsltproc)
-- 
1.7.9.5