#4 Add CPack support

[Petr Aleksandrov]

I propose to add CPack support to MathGL.
The simplest way is to add the following lines to the end of the root CMakeLists.txt (at least for support of Debian packages):
set(CPACK_PACKAGE_VERSION 2.3.2)
set(CPACK_DEBIAN_PACKAGE_MAINTAINER "<package maintaner="" name="">")
include(CPack)</package>

Setting CPACK_DEBIAN_PACKAGE_MAINTAINER is required to build Debian package.

[Petr Aleksandrov]

I have made a mistake in "set(CPACK_DEBIAN_PACKAGE_MAINTAINER ...)" due to formatting of the text.
CPACK_DEBIAN_PACKAGE_MAINTAINER must be set to the package maintainer name (in quotes).