log: Reimplement logging and debugging

This commit replaces the old rudimentary log handler
by a shinier version of it. It also introduces the
debugging macros that I usually add to the apps,
including the CC_TRACE_MSG() macro for tracing.

shell/cc-log.h

@@ -0,0 +1,25 @@
+/* cc-log.h
+ *
+ * Copyright © 2018 Georges Basile Stavracas Neto <georges.stavracas@gmail.com>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#pragma once
+
+G_BEGIN_DECLS
+
+void cc_log_init (void);
+
+G_END_DECLS