Generate Makefile with not so long lines.

Just using "cp" is incorrect, as it will overwrite old files
possibly used by OS, leading to unexpected effects.  Changed
to "mv + cp", much like used for the main binary.

The "build" target introduced to do all build-related tasks, and
it is now used in Makefile and in objs/Makefile as a dependency for
the "install" target.

In particular, this resolves problems as observed with dynamic modules
by people trying to do "make install" without calling "make" first.

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.

It's now initialized in auto/options like the rest of variables
for system paths.

As a side effect, the currently unused macro NGX_SBIN_PATH now
gets the correct value.

Parentheses are more portable, in particular they are understood by nmake
while braces aren't.