Add WINDOWS_BUILD macro to enable Windows build on *NIX host.

Add optional suffix for executables.

Fix shared object suffix logic to support multiple suffixes.

Fix soname handling to always match output.

WINDOWS macro sets WINDOWS_BUILD.

WINDOWS_BUILD sets .exe executable suffix.

WINDOWS_BUILD shared mode creates dll import library.

WINDOWS_BUILD shared mode link against dll.

Signed-off-by: Alon Bar-Lev <alon.barlev@gmail.com>