patch 8.1.0193: terminal debugger buttons don't always work

Problem:    Terminal debugger buttons don't always work. (Dominique Pelle)
Solution:   Set 'cpo' to its default value.

runtime/pack/dist/opt/termdebug/plugin/termdebug.vim

@@ -56,6 +56,9 @@ else
  finish
endif

let s:keepcpo = &cpo
set cpo&vim

" The command that starts debugging, e.g. ":Termdebug vim".
" To end type "quit" in the gdb window.
command -nargs=* -complete=file -bang Termdebug call s:StartDebug(<bang>0, <f-args>)
@@ -943,3 +946,6 @@ func s:BufUnloaded()
    endif
  endfor
endfunc

let &cpo = s:keepcpo
unlet s:keepcpo

src/version.c

@@ -789,6 +789,8 @@ static char *(features[]) =

static int included_patches[] =
{   /* Add new patch number below this line */
/**/
    193,
/**/
    192,
/**/