Cannot use escape sequences in prompt

[gwsw]

2a642a0 which fixes #503 breaks the ability to include escape sequences in prompts.

Steps to reproduce:
Run echo hello | less -R -Ps$(printf '\e[41mred\e[m')

Expected result:
Prompt should be "red", colored red.

Actual result:
Prompt is "ESC[41mredESC[m".

[gwsw]

Also breaks the "v" command when the filename contains nonprintable characters.

Steps to reproduce:

1. Run echo hello > 'tab^Ifile' where the ^I is a literal tab character
2. Run less 'tab^Ifile'
3. Type v

Expected result:
Run an editor on the file

Actual result:
Runs editor on the nonexistent file tab^Ifile, where the ^I is the two characters "^" and "I".

[gwsw]

Fixed in bf14bc4.