Fix #6518
Merge pull request #6526 from amitmurthy/amitm/6518

Fix #6518
Fix factorization for symmetric tridiagonal matrices
Fix #6509 (recognize _ in numeric literals in textmate syntax highlighting)
Merge pull request #6531 from malmaud/master

Fix #6509 (recognize _ in numeric literals in textmate syntax highlighting)
fix some issues with sparse reductions
fix error in last sparse reductions change