autoconf probe macro to determine how to use Expat.

Anonymous contribution: SF patch #438892.

expat/conftools/expat.m4

@@ -0,0 +1,43 @@
+dnl Check if --with-expat[=PREFIX] is specified and
+dnl Expat >= 1.95.0 is installed in the system.
+dnl If yes, substitute EXPAT_CFLAGS, EXPAT_LIBS with regard to
+dnl the specified PREFIX and set with_expat to PREFIX, or 'yes' if PREFIX
+dnl has not been specified. Also HAVE_LIBEXPAT, HAVE_EXPAT_H are defined.
+dnl If --with-expat has not been specified, set with_expat to 'no'.
+dnl In addition, an Automake conditional EXPAT_INSTALLED is set accordingly.
+dnl This is necessary to adapt a whole lot of packages that have expat
+dnl bundled as a static library.
+AC_DEFUN(AM_WITH_EXPAT,
+[ AC_ARG_WITH(expat,
+	      [  --with-expat=PREFIX     Use system Expat library],
+	      , with_expat=no)
+
+  AM_CONDITIONAL(EXPAT_INSTALLED, test $with_expat != no)
+
+  EXPAT_CFLAGS=
+  EXPAT_LIBS=
+  if test $with_expat != no; then
+	if test $with_expat != yes; then
+		EXPAT_CFLAGS="-I$with_expat/include"
+		EXPAT_LIBS="-L$with_expat/lib"
+	fi
+	AC_CHECK_LIB(expat, XML_ParserCreate,
+		     [ EXPAT_LIBS="$EXPAT_LIBS -lexpat"
+		       expat_found=yes ],
+		     [ expat_found=no ],
+		     "$EXPAT_LIBS")
+	if test $expat_found = no; then
+		AC_MSG_ERROR([Could not find the Expat library])
+	fi
+	expat_save_CFLAGS="$CFLAGS"
+	CFLAGS="$CFLAGS $EXPAT_CFLAGS"
+	AC_CHECK_HEADERS(expat.h, , expat_found=no)
+	if test $expat_found = no; then
+		AC_MSG_ERROR([Could not find expat.h])
+	fi
+	CFLAGS="$expat_save_CFLAGS"
+  fi
+
+  AC_SUBST(EXPAT_CFLAGS)
+  AC_SUBST(EXPAT_LIBS)
+])