[vala: 4/7] glib-2.0: add feature test macro _GNU_SOURCE for exp10(3) and exp10f(3)

[Rico Tzschichholz <ricotz src gnome org>]

commit cfa0f524d50fcbddbdabd6eb8152f45dc8dd5005
Author: Dr. Michael Lauer <mickey vanille-media de>
Date:   Mon Feb 26 17:11:39 2018 +0100

    glib-2.0: add feature test macro _GNU_SOURCE for exp10(3) and exp10f(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 56f847e..8278574 100644
--- a/vapi/glib-2.0.vapi
+++ b/vapi/glib-2.0.vapi
@@ -1573,7 +1573,9 @@ namespace GLib {
                public static float log10f (float x);
                public static double modf (double x, out double iptr);
                public static float modff (float x, out float iptr);
+               [CCode (feature_test_macro = "_GNU_SOURCE")]
                public static double exp10 (double x);
+               [CCode (feature_test_macro = "_GNU_SOURCE")]
                public static float exp10f (float x);
                [CCode (feature_test_macro = "_GNU_SOURCE")]
                public static double pow10 (double x);