library: reduce overhead for another 'escape' function

library: reduce overhead for another 'escape' function

The preceding commit made that 'esc_all' function more
efficient by using direct pointer manipulation instead
of an indexed string reference approach within a loop.

This commit applies the same approach to the 'esc_ctl'
function. Now we'll save 12 more iterated instructions
while decreasing the function's code size by 43 bytes.

Signed-off-by: Jim Warner <james.warner@comcast.net>