[folks] Version the installed backends using the LT current version number

[Travis Reitter <treitter src gnome org>]

commit 8f0befca507bd6388327e800a264628272457d1b
Author: Philip Withnall <philip withnall collabora co uk>
Date:   Fri Jul 23 13:38:53 2010 +0100

    Version the installed backends using the LT current version number
    
    This changes with every API/ABI change which is made to libfolks,
    so it should ensure that only binary compatible modules are loaded
    at runtime.

 backends/telepathy/Makefile.am |    2 +-
 configure.ac                   |   14 ++++++++++++++
 folks/Makefile.am              |    3 +--
 3 files changed, 16 insertions(+), 3 deletions(-)
---
diff --git a/backends/telepathy/Makefile.am b/backends/telepathy/Makefile.am
index a7882fd..60ed3e5 100644
--- a/backends/telepathy/Makefile.am
+++ b/backends/telepathy/Makefile.am
@@ -11,7 +11,7 @@ VALAFLAGS += --vapidir=. --vapidir=$(top_srcdir)/folks
 noinst_LTLIBRARIES = libtp-lowlevel.la
 folks_telepathydir = $(libdir)
 folks_telepathy_LTLIBRARIES = libfolks-telepathy.la
-backenddir = $(libdir)/folks/backends/telepathy
+backenddir = $(BACKEND_DIR)/telepathy
 backend_LTLIBRARIES = libfolks-backend-telepathy.la
 
 ##################################################################
diff --git a/configure.ac b/configure.ac
index 031afc4..d7eb769 100644
--- a/configure.ac
+++ b/configure.ac
@@ -28,6 +28,8 @@ m4_define(folks_maybe_datestamp,
 
 m4_define(folks_version, folks_full_version[]folks_maybe_datestamp)
 
+# Module API version.
+m4_define([folks_module_version], [folks_lt_current])
 
 AC_INIT(folks, folks_version, folks)
 m4_ifdef([AM_SILENT_RULES], [AM_SILENT_RULES([yes])])
@@ -121,6 +123,18 @@ AC_SUBST(TP_GLIB_CFLAGS)
 AC_SUBST(TP_GLIB_LIBS)
 
 # -----------------------------------------------------------
+# Backends
+# -----------------------------------------------------------
+
+FOLKS_MODULE_VERSION=folks_module_version()
+AC_SUBST(FOLKS_MODULE_VERSION)
+AC_DEFINE([MODULE_VERSION], ["folks_module_version()"],
+          [Module interface version])
+
+BACKEND_DIR='$(libdir)/folks/$(FOLKS_MODULE_VERSION)/backends'
+AC_SUBST(BACKEND_DIR)
+
+# -----------------------------------------------------------
 # Documentation
 # -----------------------------------------------------------
 AC_ARG_ENABLE(docs,
diff --git a/folks/Makefile.am b/folks/Makefile.am
index f9d3b83..1340473 100644
--- a/folks/Makefile.am
+++ b/folks/Makefile.am
@@ -1,11 +1,10 @@
 sharedir = $(datadir)/folks
-backenddir = $(libdir)/folks
 
 AM_CPPFLAGS = \
 	-include $(CONFIG_HEADER) \
 	-DPACKAGE_DATADIR=\"$(pkgdatadir)\" \
 	-DDATA_DIR=\"$(shareddir)\" \
-	-DBACKEND_DIR=\"$(backenddir)\" \
+	-DBACKEND_DIR=\"$(BACKEND_DIR)\" \
 	-DG_LOG_DOMAIN=\"Core\" \
 	$(NULL)