Signed-off-by: Piotr Sikora <piotrsikora@google.com>

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.

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.

Previously, if configured with --with-cc="clang -g", the autotest.dSYM
directories were left unremoved.

At least Sun Studio 12 has problems with bit-fields exposed by nginx code
(caught by test suite).  They seems to be fixed in Sun Studio 12.1.  As a
workaround use "-fast -xalias_level=any" for older versions, it resolves
the problem.