[PATCH] Make n_spaces return a const char *

[Tom Tromey]

>>>>> "Tom" == Tom Tromey <tom@tromey.com> writes:

Tom> n_spaces keeps the spaces in a static buffer.  If a caller overwrites
Tom> these, it may give an incorrect result to a subsequent caller.  So,
Tom> make the return type const to help avoid this outcome.

I'm checking this in now.

Sometimes I wonder if we want to split these utility things into
separate files and put them in gdbsupport.

Tom