Copyright headers: point to LICENSE.md and shorten

The following script was applied:

    sed ':a;/part of MXE.$/{N;s/\n//;ba}' -i $(git grep -l 'part of MXE')

    sed 's/\(part of MXE\).*\(See index.html\)/\1. \2/' -i \
        $(git grep -l 'part of MXE.*See index.html')

    before='This file is part of MXE. See index.html for further information.'
    after='This file is part of MXE. See LICENSE.md for licensing information.'
    sed "s/$before/$after/" -i $(git grep -l 'part of MXE')

Then git grep 'index.html for further information' revealed two other files.
One of them was patched manually (patch.mk). Makefile has text
"See index.html for further information" unrelated to licensing.

See https://github.com/mxe/mxe/issues/1500#issuecomment-241340792

1 files changed, 1 insertions, 2 deletions

diff --git a/tools/fake-editor b/tools/fake-editor
index 25a7ccf..26cc934 100755
--- a/tools/fake-editor
+++ b/tools/fake-editor
@@ -1,6 +1,5 @@
 #!/bin/sh
-# This file is part of MXE.
-# See index.html for further information.
+# This file is part of MXE. See LICENSE.md for licensing information.
 
 # Fake "editor" to format output for GitHub issue.
 # See tools/s3-fetch-and-sync for more info.