* gdb.base/step-line.exp: Check that GDB can handle filenames that

* gdb.base/step-line.exp: Check that GDB can handle filenames that
appear in the line number info, but not in the preprocessor macro
info.

* lib/gdb.exp (gdb_internal_error_regexp): New variable.
(gdb_internal_error_resync): New procedure.
(gdb_test): If the command results in an internal error,
answer GDB's questions until we get back to a prompt.