[vala] glib-2.0: add MappedFile.from_fd constructor

[Rico Tzschichholz <ricotz src gnome org>]

commit 74996a8e54a6852b4a1e281de95b6e1916040be5
Author: Christian Kellner <christian kellner me>
Date:   Tue Jul 16 18:16:52 2019 +0200

    glib-2.0: add MappedFile.from_fd constructor
    
    Add the missing 'g_mapped_file_new_from_fd' constructor, added
    with glib 2.32.
    
    Fixes https://gitlab.gnome.org/GNOME/vala/issues/824

 vapi/glib-2.0.vapi | 2 ++
 1 file changed, 2 insertions(+)
---
diff --git a/vapi/glib-2.0.vapi b/vapi/glib-2.0.vapi
index 0e1292e6b..48c0da72b 100644
--- a/vapi/glib-2.0.vapi
+++ b/vapi/glib-2.0.vapi
@@ -3784,6 +3784,8 @@ namespace GLib {
        [CCode (ref_function = "g_mapped_file_ref", unref_function = "g_mapped_file_unref")]
        public class MappedFile {
                public MappedFile (string filename, bool writable) throws FileError;
+               [Version (since = "2.32")]
+               public MappedFile.from_fd (int fd, bool writable) throws FileError;
                public size_t get_length ();
                public unowned char* get_contents ();
                [Version (since = "2.34")]