getstr() improvements
A K_NOSPACES mode - don't allow any whitespace in string console.getstr() could return a Number (rather than String) when in K_NUMBER mode.
console.getstr() could return false/null/undefined if Ctrl-C is hit, rather than returning an empty or unmodified string.
sbbs_t::getstr() could return -1 on abort (rather than 0) - risky change.