added section "Common problems" to 'dredge' help page

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/mumin@279 edb9625f-4e0d-4859-8d74-9fd3b1da38cb
new function 'matmult' for matrix multiplication with option for calculating only the diagonal.
modified r.squaredGLMM to use 'matmult'

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/mumin@280 edb9625f-4e0d-4859-8d74-9fd3b1da38cb
new package files 1.10.4

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/mumin@281 edb9625f-4e0d-4859-8d74-9fd3b1da38cb