changes & fixes to %*%, crossprod(),.. notably for diagonal matrices

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/matrix@2998 edb9625f-4e0d-4859-8d74-9fd3b1da38cb
fix/speed up coercions from/to symmetric/triangular

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/matrix@2999 edb9625f-4e0d-4859-8d74-9fd3b1da38cb
"Math" and "Summary" methods now put in one (newly created) file; more tests for these..

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/matrix@3000 edb9625f-4e0d-4859-8d74-9fd3b1da38cb