Unportable test(1) operator

The configure script uses "==" as a test comparison operator. This is not portable, only bash supports it.

Fix: In configure.ac replace

    AS_IF([test "$with_ssl" == "yes"], [AC_MSG_ERROR([*** No SSL/TLS library not found.])],

with

    AS_IF([test "$with_ssl" = "yes"], [AC_MSG_ERROR([*** No SSL/TLS library not found.])],