guile: support version 3.0.

Includes an update to the guile m4 package, and tweaks the build so that
both 2.2 and 3.0 should work fine.

configure.ac

@@ -212,22 +212,22 @@ AM_CONDITIONAL(BUILD_GUI,[test "x$have_webkit" = "xyes" -a "x$have_gtk" = "xyes"
 ###############################################################################
 
 ###############################################################################
-# build with guile2.2 when available and not disabled.
+# build with guile 3.0/2.2 when available and not disabled.
 AC_ARG_ENABLE([guile], AS_HELP_STRING([--disable-guile],[Disable guile]))
 AS_IF([test "x$enable_guile" != "xno"],[
-  PKG_CHECK_MODULES(GUILE22, guile-2.2, [have_guile22=yes],[have_guile22=no])
-  # this is a bit hacky; GUILE_PKG
-  AS_IF([test "x$have_guile22" = "xyes"],[
-    GUILE_PKG([2.2])
+  PKG_CHECK_MODULES(GUILE, [guile-3.0], [have_guile=yes],[
+    PKG_CHECK_MODULES(GUILE, [guile-2.2], [have_guile=yes], [have_guile=no])])
+  AS_IF([test "x$have_guile" = "xyes"],[
+    GUILE_PKG([3.0 2.2])
     GUILE_PROGS
     GUILE_FLAGS
     AC_DEFINE_UNQUOTED([GUILE_BINARY],"$GUILE",[guile binary])
     AC_DEFINE(BUILD_GUILE,[1], [Do we support Guile?])
     AC_SUBST(GUILE_SNARF, [guile-snarf])
-    guile_version=$($PKG_CONFIG guile-2.2 --modversion)
+    guile_version=$($PKG_CONFIG guile-$GUILE_EFFECTIVE_VERSION --modversion)
   ])
 ])
-AM_CONDITIONAL(BUILD_GUILE,[test "x$have_guile22" = "xyes"])
+AM_CONDITIONAL(BUILD_GUILE,[test "x$have_guile" = "xyes"])
 ###############################################################################
 
 ###############################################################################

guile/Makefile.am

@@ -69,7 +69,7 @@ SUFFIXES = .x .doc
 
 # FIXME: GUILE_SITEDIR would be better, but that
 # breaks 'make distcheck'
-scmdir=${prefix}/share/guile/site/2.2/
+scmdir=${prefix}/share/guile/site/${GUILE_EFFECTIVE_VERSION}
 scm_DATA=mu.scm
 
 EXTRA_DIST=$(scm_DATA)

guile/mu/Makefile.am

@@ -16,9 +16,7 @@
 
 include $(top_srcdir)/gtest.mk
 
-# FIXME: GUILE_SITEDIR would be better, but that
-# breaks 'make distcheck'
-scmdir=${prefix}/share/guile/site/2.2/mu/
+scmdir=${prefix}/share/guile/site/${GUILE_EFFECTIVE_VERSION}/mu/
 
 scm_DATA=		\
 	stats.scm	\

m4/Makefile.am

@@ -41,7 +41,7 @@ EXTRA_DIST=				\
 	ax_lib_readline.m4		\
 	ax_require_defined.m4		\
 	ax_valgrind_check.m4		\
-	guile-2.2.m4			\
+	guile.m4			\
 	lib-ld.m4			\
 	lib-link.m4			\
 	lib-prefix.m4

m4/guile.m4

@@ -47,8 +47,8 @@
 # for an available version of Guile.
 #
 # By default, this macro will search for the latest stable version of
-# Guile (e.g. 2.2), falling back to the previous stable version
-# (e.g. 2.0) if it is available.  If no guile-@var{VERSION}.pc file is
+# Guile (e.g. 3.0), falling back to the previous stable version
+# (e.g. 2.2) if it is available.  If no guile-@var{VERSION}.pc file is
 # found, an error is signalled.  The found version is stored in
 # @var{GUILE_EFFECTIVE_VERSION}.
 #
@@ -60,8 +60,11 @@
 # @code{AC_SUBST}.
 #
 AC_DEFUN([GUILE_PKG],
- [PKG_PROG_PKG_CONFIG
-  _guile_versions_to_search="m4_default([$1], [2.2 2.0 1.8])"
+ [AC_REQUIRE([PKG_PROG_PKG_CONFIG])
+  if test "x$PKG_CONFIG" = x; then
+    AC_MSG_ERROR([pkg-config is missing, please install it])
+  fi
+  _guile_versions_to_search="m4_default([$1], [3.0 2.2 2.0])"
   if test -n "$GUILE_EFFECTIVE_VERSION"; then
     _guile_tmp=""
     for v in $_guile_versions_to_search; do
@@ -221,7 +224,7 @@ AC_DEFUN([GUILE_SITE_DIR],
 # as well.
 #
 # By default, this macro will search for the latest stable version of
-# Guile (e.g. 2.2). x.y or x.y.z versions can be specified. If an older
+# Guile (e.g. 3.0). x.y or x.y.z versions can be specified. If an older
 # version is found, the macro will signal an error.
 #
 # The effective version of the found @code{guile} is set to
@@ -237,7 +240,7 @@ AC_DEFUN([GUILE_SITE_DIR],
 AC_DEFUN([GUILE_PROGS],
  [_guile_required_version="m4_default([$1], [$GUILE_EFFECTIVE_VERSION])"
   if test -z "$_guile_required_version"; then
-    _guile_required_version=2.2
+    _guile_required_version=3.0
   fi
 
   _guile_candidates=guile