CMake: Use upstream CheckTypeSize module

The CheckTypeSize module that comes with CMake 2.6.2 and above does
everything we need and also supports cross-compiling.  Avoid duplicating
an older version of it here.  This also fixes a cross-compiling error
because the old line

  include ("${CMAKE_MODULE_PATH}/CheckTypeSize.cmake")

failed because CMAKE_MODULE_PATH is a search path and not a directory.

Signed-off-by: Brad King <brad.king@kitware.com>