module: Support for loading of modules

A module is a shared library existing in, or a subdirectory of, the
module directory. The directory is by default
${libdir}/pinos-$(MAJORMINOR)/modules, but can be specified with
--with-module-dir=PATH when running configure. It is also possible to
override the module directory runtime with the environment variable
PINOS_MODULE_DIR, which is a list of directories separated with ":".

pinos/daemon/main.c

@@ -18,10 +18,12 @@
  */
 
 #include <gio/gio.h>
+#include <glib.h>
 #include <gst/gst.h>
 
 #include <client/pinos.h>
 #include <server/daemon.h>
+#include <server/module.h>
 #include <modules/gst/gst-manager.h>
 #include <modules/gst/gst-node-factory.h>
 #include <spa/include/spa/memory.h>