Addition of gstreamer importer support. Will only use system

libraries...no locals for this fella.

gstreamer-1.0 is required.

m4/audacity_checklib_gstreamer.m4

@@ -0,0 +1,42 @@
+dnl add license?
+dnl
+dnl Please increment the serial number below whenever you alter this macro
+dnl for the benefit of automatic macro update systems
+# audacity_checklib_gstreamer.m4 serial 3
+
+AC_DEFUN([AUDACITY_CHECKLIB_GSTREAMER], [
+
+   AC_ARG_WITH(gstreamer,
+               [AS_HELP_STRING([--with-gstreamer],
+                               [include gstreamer import/export support])],
+               GSTREAMER_ARGUMENT=$withval,
+               GSTREAMER_ARGUMENT="unspecified")
+
+   dnl see if gstreamer is installed on the system
+
+   PKG_CHECK_MODULES(GSTREAMER, gstreamer-1.0 gstreamer-app-1.0,
+                     GSTREAMER_SYSTEM_AVAILABLE="yes",
+                     GSTREAMER_SYSTEM_AVAILABLE="no")
+
+   if test "$GSTREAMER_SYSTEM_AVAILABLE" = "yes"; then
+      AC_MSG_NOTICE([gstreamer libraries are available as system libraries])
+   else
+      AC_MSG_NOTICE([gstreamer libraries are NOT available as system libraries])
+   fi
+
+   GSTREAMER_LOCAL_AVAILABLE="no"
+])
+
+AC_DEFUN([AUDACITY_CONFIG_GSTREAMER], [
+
+   AC_SUBST([GSTREAMER_CFLAGS])
+   AC_SUBST([GSTREAMER_LIBS])
+
+   AM_CONDITIONAL([USE_GSTREAMER], [test "$GSTREAMER_USE_SYSTEM" = yes])
+
+   if test "$GSTREAMER_USE_SYSTEM" = yes; then
+      AC_DEFINE(USE_GSTREAMER, 1,
+                [Define if the gstreamer is present])
+   fi
+
+])