Merge of r4948, r4949, r4964, r4973, r5011: variables. *) Allow the complex value to be defined as an empty string. This makes conversion from strings to complex values possible without the loss of functionality. *) The "auth_basic" directive gained support of variables. *) Fixed variable syntax checking in "set", "geo", "limit_conn_zone", and "perl_set" directives. *) Added checks that disallow adding a variable with an empty name. Added variable name syntax checks to "geo" and "map" directives. *) Variables $pipe, $request_length, $time_iso8601, and $time_local. Log module counterparts are preserved for efficiency. Based on patch by Kiril Kalchev.