Add --with-relocated-sources configure option

[Tom Tromey]

>>>>> "Joseph" == Joseph S Myers <joseph@codesourcery.com> writes:

Joseph> +AC_HELP_STRING([--with-relocated-sources=path], [Automatically relocate this path for source files]),

I missed this last time, but since you are getting another doc review
I thought I would point it out: `=path' should be `=PATH' here,
according to GNU rules.

I see a couple of places in configure --help that don't do this
properly.  I will fix those shortly.

Tom