parallels: build with parallels SDK

parallels: build with parallels SDK

Executing prlctl command is not an optimal way to interact with
Parallels Cloud Server (PCS), it's better to use parallels SDK,
which is a remote API to paralles dispatcher service.

We prepared opensource version of this SDK and published it on
github, it's distributed under LGPL license. Here is a git repo:
https://github.com/Parallels/parallels-sdk.

To build with parallels SDK user should get compiler and linker
options from pkg-config 'parallels-sdk' file. So fix checks in
configure script and build with parallels SDK, if that pkg-config
file exists and add gcc options to makefile.

Signed-off-by: Dmitry Guryanov <dguryanov@parallels.com>