Support spaces in vars values parsed through set_var()

This changes how the eval call in set_var() gets passed the value. It
now quotes the remainder of the arguments passed, allowing for a space
in the value. As a small bonus, values no longer need to be quoted in
the vars file, though this is still good practice.
Always export OPENSSL_CONF to the value of SSL_CONFIG

This prevents a pre-existing OPENSSL_CONF env-var from showing the very
warning this attempts to stop.
Remove win32.shell support

The Windows component will use mksh, removing the need to work around
the Cygwin warning for Win32 paths.
Use PWD env-var instead of the pwd subshell command
Fix extra break level that is unnecessary
gen_req() no longer makes REQ_CN func-local

This fix is needed to operate properly in at least the mksh shell.