[RFAv2 0/3] new args [-dirname | -basename] [--] [REGEXP] to info sources

[Philippe Waroquiers <philippe dot waroquiers at skynet dot be>]

This patch series adds the arguments [-dirname | -basename] [--] [REGEXP] to
the command "info sources".

Currently, info sources shows the name of all source files.
For big programs, the list can be very long, which means the prompt
to continue kicks in.

These optional new arguments allow to have a more selective way to print
the source file names.

This is the second version of the patch series.

Compared to the first version:
  * As suggested by Tom, the command now uses the new cli option -OPT
    framework.  Options -dirname and -basename are replacing -d and -b.
  * gdb/testsuite/gdb.base/info_sources.exp changed to test the new
    options names, using short or longer parts of the option names.
  * The documentation and NEWS have been updated accordingly.
    The comments given by Eli were also handled.