2.6.1: patch / add option -S, --simulate

[Jari Aalto]

It would be nice if the applicability of patch could be tested before it is
actually applied. With patches that span multiple files this is even more
handy.

The git-apply(1) command contains option --check to simulate applying a
patch. It's output looks like:

    warning: src/Config.tmpl_solaris has type 100755, expected 100644
    warning: src/Config.tmpl_solaris.gcc has type 100755, expected 100644
    warning: src/Config.tmpl_sunos has type 100755, expected 100644
    error: src/Makefile: wrong type
    error: patch failed: src/dg/Makefile:141
    error: src/dg/Makefile: patch does not apply

I'm proposing similar functionality:

    warning: For fuzz hunks
    error: for failures

to be added to patch(1) as well. The possible options could be:

    -S, --simulate

Jari