* mi-regs.exp: Various cleanups for SPARC-only tests.

* mi-regs.exp: Various cleanups for SPARC-only tests.
(test_breakpoints_creation_and_listing): Format of breakpoint
table has changed.
(sparc_register_tests): Expand floating-point number regexp to
recognize NaN values, too.  Replace ineffectual single backslash
before a hyphen with a double backslash.  Don't check the exact
numbers of the registers which have changed, since there's no way
to know which registers changed, exactly; just check that the
result is well-formed.
* mi0-regs.exp: (sparc_register_tests): Same as for
sparc_register_tests in mi-regs.exp.