m4 check for OpenSSL does not consider multi-arch setups

[victor jimenez]

In distributions that use multi-arch setup (such as Debian 7) libssl.a is
installed in /usr/lib/x86_64-linux-gnu. That renders the m4
macro ax_check_openssl.m4 useless for such systems since the library is
only looked for in the following paths:

ssldirs="/usr/local/ssl /usr/lib/ssl /usr/ssl /usr/pkg /usr/local /usr"

Boost is also installed in /usr/lib/x86_64-linux-gnu, but the m4 macro for
Boost takes care of it in the following way:

100 dnl allow for real multi-arch paths e.g. /usr/lib/x86_64-linux-gnu.
Give 101 dnl them priority over the other paths since, if libs are found
there, they 102 dnl are almost assuredly the ones desired. 103
AC_REQUIRE([AC_CANONICAL_HOST]) 104 libsubdirs="lib/${host_cpu}-${host_os}
$libsubdirs" 105 106 case ${host_cpu} in 107 i?86) 108
libsubdirs="lib/i386-${host_os} $libsubdirs" 109 ;; 110 esac

My knowledge of m4 and autoconf's internals is very limited, so it would be
great if someone with the required knowledge could have a look at it. But I
may be able to come up with a solution if I receive some guidance.

Thank you,
Victor