[vala: 2/7] glib-2.0: add feature test macro _GNU_SOURCE for pow10(3) and pow10f(3)

[Rico Tzschichholz <ricotz src gnome org>]

commit 9f5773ffda0481f4402a5abe66672d153221a7e2
Author: Dr. Michael Lauer <mickey vanille-media de>
Date:   Mon Feb 26 17:02:00 2018 +0100

    glib-2.0: add feature test macro _GNU_SOURCE for pow10(3) and pow10f(3)
    
    https://bugzilla.gnome.org/show_bug.cgi?id=614788

 vapi/glib-2.0.vapi |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)
---
diff --git a/vapi/glib-2.0.vapi b/vapi/glib-2.0.vapi
index e6732c5..56f847e 100644
--- a/vapi/glib-2.0.vapi
+++ b/vapi/glib-2.0.vapi
@@ -1575,7 +1575,9 @@ namespace GLib {
                public static float modff (float x, out float iptr);
                public static double exp10 (double x);
                public static float exp10f (float x);
+               [CCode (feature_test_macro = "_GNU_SOURCE")]
                public static double pow10 (double x);
+               [CCode (feature_test_macro = "_GNU_SOURCE")]
                public static float pow10f (float x);
                public static double expm1 (double x);
                public static float expm1f (float x);