adjusted the g_strdup_a, g_strndup_a and g_strconcat3_a macros so their

adjusted the g_strdup_a, g_strndup_a and g_strconcat3_a macros so their

Mon Jan  4 14:38:11 1999  Tim Janik  <timj@gtk.org>

        * glib.h: adjusted the g_strdup_a, g_strndup_a and g_strconcat3_a macros
        so their arguments get only evaluated once. changed g_strconcat3_a to
        have the same semantics as g_strconcat, i.e. if a certain argument is
        NULL, the rest of the parameter list is skipped.

        * tests/alloca-test.c: removed #if/#endif G_HAVE_ALLOCA, we need to be
        able to compile on all systems. added test for g_strconcat() semantics.

        * we need a alloca() replacement for !G_HAVE_ALLOCA rsn!