send-email: do not barf when Term::ReadLine does not like your terminal

send-email: do not barf when Term::ReadLine does not like your terminal

As long as we do not need to readline from the terminal, we
should not barf when starting up the program.  Without this
patch, t9001 test on Cygwin occasionally died with the following
error message:

Unable to get Terminal Size. The TIOCGWINSZ ioctl didn't work. The COLUMNS and LINES environment variables didn't work. The resize program didn't work. at /usr/lib/perl5/vendor_perl/5.8/cygwin/Term/ReadKey.pm line 362.
Compilation failed in require at /usr/lib/perl5/vendor_perl/5.8/Term/ReadLine/Perl.pm line 58.

Acked-by: Ryan Anderson <ryan@michonline.com>
Signed-off-by: Junio C Hamano <junkio@cox.net>