First steps towards removing glib dependencies

- remove the build flags and libraries from the Makefile / Configure.mk
- remove the glib types (gboolean, gchar, gint64, gint)
- comment out / hack around gettext
- replace the glib file helper functions
- replace g_ascii_strtod
- replace g_build_filename
- use environment variables instead of g_get_home_dir() & g_get_user_name()
- comment out GPS string parsing (uses glib utf8 macros)

This needs massive cleanup, but it's a snapshot of what I have right now, in
case people want to look at it.

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>

deco.c

@@ -249,7 +249,7 @@ double restore_deco_state(char *data)
 	return tissue_tolerance;
 }
 
-unsigned int deco_allowed_depth(double tissues_tolerance, double surface_pressure, struct dive *dive, gboolean smooth)
+unsigned int deco_allowed_depth(double tissues_tolerance, double surface_pressure, struct dive *dive, bool smooth)
 {
 	unsigned int depth;
 	double pressure_delta;