telnet: code shrink

function                                             old     new   delta
telnet_main                                         1519    1515      -4
con_escape                                           296     285     -11

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
Fix build failures caused by not compiling open_transformer.c

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
hush: fix build failure if FEATURE_EDITING=y && !HUSH_INTERACTIVE

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