Source package provided by upstream contains embedded Boost source code,
needed to build PyCUDA under Microsoft Windows and Mac OS X.  I have
decided to write get-orig-source rule in debian/rules instead of
repackaging upstream source.

debian/rules get-orig-source retrieves all the source files needed to
build PyCUDA from git repositories and builds pycuda_*.orig.tar.gz.
get-orig-source downloads both PyCUDA and compyte; compyte is managed
as PyCUDA submodule in git and contains code for managing GPU-based
arrays common for PyCUDA and PyOpenCL.

get-orig-source behaviour is governed by following variables, defined
in debian/make
 * GIT_URL - git repository from which to download source
 * GIT_SUBMODULES - list of git submodules to download; upstream repository
   contains two submodules (boost and compyte) and get-orig-source
   retrieves on of them (compyte)
 * GIT_REVISION - git revision to retrieve; you can change it to get
   different revision, for example for debugging purposes.
