patch: fix for autoconf ssl checking

[wil <wil dready org>]

When doing "./configure --with-ssl" the script would enable SSL support
because it doesn't perform any check to verify it. When doing
AC_CONFIG_SUBDIRS(libmutt), it passes the same argument to the configure
script, i.e. "--with-ssl" but libmutt requires --with-ssl=DIR unless your
openssl is installed in standard prefixes like "/usr".  This fixes the
problem as many of us hand-compiled openssl and by defaults it gets
installed into /usr/local/ssl.

This patch tries to find the ssl prefix by searching a few directories
(ripped this off from stunnel's configure.in script), then stores it in a
cache variable which is retrieved by libmutt's configure script.

Thanks.

wil.

ac_ssl.diff