[Ada] use lbasename when testing if file is part of Ada runtime.

[Ada] use lbasename when testing if file is part of Ada runtime.

We use a list of regular expressions to match a symtab filenames
against the names of the files in the Ada runtime.  These regular
expressions do assume that the filename is a basename, however.
So make sure to evaluate these regular expressions against
the symtab's filename.

Without this patch, we run into problems when the Ada runtime was built
using a project file (through gprbuild).

gdb/ChangeLog:

        * ada-lang.c (is_known_support_routine): Use lbasename when
        matching the symtab's filename against
        known_runtime_file_name_patterns.