This removes the print_spaces helper function, in favor of using the
"*%s" idiom that's already used in many places in gdb. One spot (in
symmisc.c) is changed to use print_spaces_filtered, because the rest
of that function is using filtered output. (This highlights one way
that the printf idiom is better -- this error is harder to make when
using that.)
Regression tested on x86-64 Fedora 34.