hush: do not drop backslash from eval 'echo ok\'

newer bash does not drop it, most other shells too

function                                             old     new   delta
unbackslash                                           39      57     +18
parse_stream                                        2753    2751      -2
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 1/1 up/down: 18/-2)              Total: 16 bytes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
6 files changed