[valadoc] gtkdoc: Don't use 'stderr' as variable name

[Rico Tzschichholz <ricotz src gnome org>]

commit 78e691a227f22080937fcbcdaacdc0e66b2444f7
Author: Jasper Lievisse Adriaanse <jasper openbsd org>
Date:   Tue Sep 5 13:07:25 2017 +0200

    gtkdoc: Don't use 'stderr' as variable name
    
    It might clash with the definition in stdio.h, e.g. on OpenBSD.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=787305

 src/doclets/gtkdoc/doclet.vala |   10 +++++-----
 1 files changed, 5 insertions(+), 5 deletions(-)
---
diff --git a/src/doclets/gtkdoc/doclet.vala b/src/doclets/gtkdoc/doclet.vala
index 2d000f6..d567d6f 100644
--- a/src/doclets/gtkdoc/doclet.vala
+++ b/src/doclets/gtkdoc/doclet.vala
@@ -283,21 +283,21 @@ public class Gtkdoc.Director : Valadoc.Doclet, Object {
                pc_libs += "--libs";
 
                try {
-                       string stderr;
+                       string stderr_buf;
                        int status;
 
                        string cflags;
-                       Process.spawn_sync (null, pc_cflags, null, SpawnFlags.SEARCH_PATH, null, out cflags, 
out stderr, out status);
+                       Process.spawn_sync (null, pc_cflags, null, SpawnFlags.SEARCH_PATH, null, out cflags, 
out stderr_buf, out status);
                        if (status != 0) {
-                               reporter.simple_error ("GtkDoc", "pkg-config cflags error: %s", stderr);
+                               reporter.simple_error ("GtkDoc", "pkg-config cflags error: %s", stderr_buf);
                                return false;
                        }
                        cflags = cflags.strip ();
 
                        string libs;
-                       Process.spawn_sync (null, pc_libs, null, SpawnFlags.SEARCH_PATH, null, out libs, out 
stderr, out status);
+                       Process.spawn_sync (null, pc_libs, null, SpawnFlags.SEARCH_PATH, null, out libs, out 
stderr_buf, out status);
                        if (status != 0) {
-                               reporter.simple_error ("GtkDoc", "pkg-config libs error: %s", stderr);
+                               reporter.simple_error ("GtkDoc", "pkg-config libs error: %s", stderr_buf);
                                return false;
                        }