Added consts to the coxph_data class of ProbABEL.

This change also involves some code layout changes in the .h file and a small fix in the Doxygen documentation of coxph_data::update_snp.


git-svn-id: svn://svn.r-forge.r-project.org/svnroot/genabel@1708 edb9625f-4e0d-4859-8d74-9fd3b1da38cb
Replace the masked_data pointer to array in the coxph_data class to a std::vector() like we did in the regadata class.

Also added a few more consts.


git-svn-id: svn://svn.r-forge.r-project.org/svnroot/genabel@1709 edb9625f-4e0d-4859-8d74-9fd3b1da38cb
regdata::get_unmasked_data() is a const member function, like its cousin in the choxph_data class.


git-svn-id: svn://svn.r-forge.r-project.org/svnroot/genabel@1710 edb9625f-4e0d-4859-8d74-9fd3b1da38cb