prepare for checking in autogenerated files

We plan to check in automatically generated files (config.h.in, etc) on
release branches. These files are normally ignored by .gitignore, but
this shuffles the contents of this file to make it easy to un-ignore
them.

.gitignore

@@ -1,18 +1,14 @@
 Makefile
 buildpkg.sh
 config.h
-config.h.in
 config.h.in~
 config.log
 config.status
-configure
-aclocal.m4
 openbsd-compat/Makefile
 openbsd-compat/regress/Makefile
 openssh.xml
 opensshd.init
 survey.sh
-**/*.0
 **/*.o
 **/*.lo
 **/*.so
@@ -36,3 +32,10 @@ sshd
 !regress/misc/fuzz-harness/Makefile
 !regress/unittests/sshsig/Makefile
 tags
+
+# Ignored on main branch
+config.h.in
+configure
+aclocal.m4
+ChangeLog
+**/*.0