Add missing '$' for variable expansion in depout.m4

[Gavin Smith]

(I hope I have prepared this patch properly.)

    Add missing '$' for variable expansion in depout.m4

    * m4/depout.m4: "am__include" appeared where "$am__include" was meant.

diff --git a/m4/depout.m4 b/m4/depout.m4
index 880a597..c79d04b 100644
--- a/m4/depout.m4
+++ b/m4/depout.m4
@@ -40,7 +40,7 @@ AC_DEFUN([_AM_OUTPUT_DEPENDENCY_COMMANDS],
     DEPDIR=`sed -n 's/^DEPDIR = //p' < "$mf"`
     test -z "$DEPDIR" && continue
     am__include=`sed -n 's/^am__include = //p' < "$mf"`
-    test -z "am__include" && continue
+    test -z "$am__include" && continue
     am__quote=`sed -n 's/^am__quote = //p' < "$mf"`
     # Find all dependency output files, they are included files with
     # $(DEPDIR) in their names.  We invoke sed twice because it is the