[gdb/testsuite, tclint] Fix gdb.dap

Running tclint on gdb.dap shows these warnings:
...
bt-nodebug.exp:74:16: namespace eval received an argument with a \
  substitution, unable to parse its arguments [command-args]
eof.exp:33:1: expected braced word or word without substitutions in argument \
  interpreted as script [command-args]
eof.exp:34:1: expected braced word or word without substitutions in argument \
  interpreted as script [command-args]
...

The first one is for:
...
set list_form [namespace eval ton::2list $last_ton]
...

I don't think this can be fixed by rewriting into something similar, so ignore
this.  Likewise in lib/dap-support.exp.

The second and third ones are for:
...
catch "close -i $gdb_spawn_id"
catch "wait -i $gdb_spawn_id"
...
which can easily be fixed by using curly braces instead of double quotes, but
doing so gets us:
...
eof.exp:33:8: unrecognized argument for close: -i [command-args]
...

This is because tclint doesn't have support for expect yet [1], so ignore this.

While we're at it, fix some trailing whitespace in lib/dap-support.

Approved-By: Tom Tromey <tom@tromey.com>

[1] https://github.com/nmoroze/tclint/issues/118