Fallback for manual setup of GTK 1, if autoconf is run on a system

where the GTK1 detection function AM_PATH_GTK hasn't been provided by
/usr/share/aclocal/gtk.m4 or equivalent.

(Systems without gtk.m4 are becoming more common, but on the other
hand I know at least one person is still using GTK 1 PuTTY since the
0.62 release.)

[originally from svn r9868]

unix/configure.ac

@@ -85,7 +85,15 @@ case "$gtk_version_desired:$gtk" in
   1:none | any:none)
     ifdef([AM_PATH_GTK],[
     AM_PATH_GTK([1.2.0], [gtk=1], [])
-    ],[AC_WARNING([generating configure script without GTK 1 autodetection])])
+    ],[
+    # manual check for gtk1
+    AC_PATH_PROG(GTK1_CONFIG, gtk-config, absent)
+    if test "$GTK1_CONFIG" != "absent"; then
+      GTK_CFLAGS=`"$GTK1_CONFIG" --cflags`
+      GTK_LIBS=`"$GTK1_CONFIG" --libs`
+      gtk=1
+    fi
+    ])
     ;;
 esac