[win32] link against ws2_32.lib
[win32] fix building libhts

compile net_winsock.c instead of net_posix.c
don't add -std=c99 -fPIC C flags
add lib/libhts/Win32/include as an include directory
fixed: use lower case kodiplatform variables
Merge pull request #1 from Montellese/win32

Support building on win32