src/psl.c: Make code compilable on native Windows
src/psl.c: Make code compilable on native Windows

Include the Windows/Winsock2 counterparts of the networking headers on
Windows and avoid including *NIX-specific headers on Windows.

Also remove the small bits of C99isms from the code.

dago/libpsl,dago/libpsl,rockdaboot/libpsl,dago/libpsl,rockdaboot/libpsl,rockdaboot/libpsl