Avoid non-posix \|-operator in sed regexp.

ChangeLog

+2012-10-29  Niels Möller  <nisse@lysator.liu.se>
+
+	From Martin Storsjö:
+	* configure.ac (dummy-dep-files): Avoid non-posix \|-operator in
+	sed regexp.
+
 2012-10-29  Niels Möller  <nisse@lysator.liu.se>
 
 	* x86_64/salsa20-core-internal.asm: New file.

configure.ac

@@ -122,7 +122,7 @@ if test x$enable_dependency_tracking = xyes ; then
 
   AC_CONFIG_COMMANDS([dummy-dep-files],
   [(cd "$srcdir" && find . '(' -name '*.c' -o -name '*.cxx' ')' -print) \
- | sed 's/\.c\(xx\|\)$//' | (while read f; do echo > "$f.o.d"; echo > "$f.po.d"; done)
+ | sed 's/\.c\(xx\)\{0,1\}$//' | (while read f; do echo > "$f.o.d"; echo > "$f.po.d"; done)
 ])
 fi