Add files parallels_sdk.c and parallels_sdk.h for code
which works with SDK, so libvirt's code will not mix with
dealing with parallels SDK.

To use Parallels SDK you must first call PrlApi_InitEx function,
and then you will be able to connect to a server with
PrlSrv_LoginLocalEx function. When you've done you must call
PrlApi_Deinit. So let's call PrlApi_InitEx on first .connectOpen,
count number of connections and deinitialize, when this counter
becomes zero.
Signed-off-by: NDmitry Guryanov <dguryanov@parallels.com>