- build_matlab.m: mwSignedIndex actually appeared in Matlab 7.3 (like mwSize and mwIndex)
- mjdgges.c: use a typedef instead of a #define for mwSignedIndex


git-svn-id: https://www.dynare.org/svn/dynare/trunk@2540 ac1d8469-bf42-47a9-8791-bf33cf982152