Optimize the common cases (init == NULL or init == "") a bit. replace uses

Optimize the common cases (init == NULL or init == "") a bit. replace uses

2003-03-30  Matthias Clasen  <maclas@gmx.de>

	* glib/gstring.c (g_string_new): Optimize the common cases
	(init == NULL or init == "") a bit.
	* glib/gmarkup.c, glib/gmessages.c, glib/gscanner.c,
	glib/gshell.c, glib/gspawn-win32-helper.c, glib/gspawn-win32.c,
	glib/gspawn.c, gobject/gvaluetransform.c: replace uses of
	g_string_new ("") by g_string_new (NULL).  (#106973, Morten Welinder)