[R-sig-Geo] followup on rgdal - invalid alignment error

[Tim Keitt]

I found the type size defs in Rinternals.h. They are
R_XDR_INTEGER_SIZE and R_XDR_DOUBLE_SIZE. I've added a check in rgdal
to ensure that type sizes match up.

THK

-- 
Timothy H. Keitt
http://www.keittlab.org/