next try to fix --with-perl_modules_path= for unpriviliged user installation

unsupported threaded environment, but now they complicate code:
*) perl_clone() requires at least duplicating nginx stash;
*) the multiplicity requires to re-evalute all precompiled subroutines
   and nginx stash in new interpreter context.

    *) Change in internal API: the HTTP modules initialization was moved
       from the init module phase to the HTTP postconfiguration phase.

    *) Change: now the request body is not read beforehand for the
       ngx_http_perl_module: it's required to start the reading using the
       $r->has_request_body method.

    *) Feature: the ngx_http_perl_module supports the DECLINED return code.

    *) Feature: the ngx_http_dav_module supports the incoming "Date" header
       line for the PUT method.

    *) Feature: the "ssi" directive is available inside the "if" block.

    *) Bugfix: a segmentation fault occurred if there was an "index"
       directive with variables and the first index name was without
       variables; the bug had appeared in 0.1.29.