added --with-pkg-config-path option try not to run autoheader too much

Original commit message from CVS:
* added --with-pkg-config-path option
* try not to run autoheader too much

autogen.sh

@@ -158,6 +158,8 @@ autoheader || {
 	echo "autoheader failed"
 	exit 1
 }
+# touch the stamp-h.in build stamp so we don't re-run autoheader in maintainer mode -- wingo
+echo timestamp > stamp-h.in 2> /dev/null
 echo "+ running autoconf ... "
 autoconf || {
 	echo

configure.ac

@@ -104,6 +104,11 @@ dnl ##############################
 dnl Check for tools:
 dnl ================
 
+dnl modify pkg-config path
+AC_ARG_WITH(pkg-config-path, 
+   AC_HELP_STRING([--with-pkg-config-path],[colon-separated list of pkg-config(1) dirs]),
+   [export PKG_CONFIG_PATH=${withval}])
+
 dnl Check for nasm
 AC_PATH_PROG(NASM_PATH, nasm, no)
 AC_SUBST(NASM_PATH)