Check 0.13.0

This release improved CMake support with a few other minor improvements.

Changes:

• configure: optional build documentation
  Issue #206 (GitHub)

• missing <unistd.h> in some files
  Issue #196 and Issue #186 (GitHub)

• Various documentation improvements

• END_TEST is now optional, as how START_TEST works has been redone
  Issue #158

• Various CMake related changes:

  • Support exporting Check to other projects with CMake 3
    Issue #185
  • Shared library support for Visual Studio
    Issue #220
  • Fix wrong library filename
    Issue #226
  • Add support for CMake package registry
    Issue #227
  • CMake build type can now be debug or release
    Issue #228
  • Add checkmk to CMake build.