githooks documentation: add a note about the +x mode
githooks documentation: add a note about the +x mode

In a freshly initialized repo it is only necessary to rename the .sample
hooks, but when using older repos (initialized with older git init)
enabled the +x mode is still necessary - docuement this.

Signed-off-by: Miklos Vajna <16f13092e03e3d9e997de904d0f86cc803fb6ef7@frugalware.org>
Signed-off-by: Junio C Hamano <a6723cc3f76163bf7adb636a73ac3b0ceb3e6b9b@pobox.com>

destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git