This is a port of corresponding http code with unrelated features excluded.

This reduces the number of moving parts in ABI compatibility checks.
Additionally, it also allows to use OpenSSL in FIPS mode while still
using md5 for non-security tasks.

It's not used and contradicts the idea of dynamic loading.

The auto/module script is extended to understand ngx_module_link=DYNAMIC.
When set, it links the module as a shared object rather than statically
into nginx binary.  The module can later be loaded using the "load_module"
directive.

New auto/module parameter ngx_module_order allows to define module loading
order in complex cases.  By default the order is set based on ngx_module_type.

3rd party modules can be compiled dynamically using the --add-dynamic-module
configure option, which will preset ngx_module_link to "DYNAMIC" before
calling the module config script.

Win32 support is rudimentary, and only works when using MinGW gcc (which
is able to handle exports/imports automatically).

In collaboration with Ruslan Ermilov.

This script simplifies configuration of additional modules,
including 3rd party ones.  The script is extensible, and
will be used to introduce dynamic linking of modules in upcoming
changes.

3rd party module config scripts are called with ngx_module_link
preset to "ADDON" - this allows config scripts to call auto/module
without ngx_module_link explicitly defined, as well as testing if
new interface is in place if compatibility with older nginx versions
is desired.

In collaboration with Ruslan Ermilov.