vim-patch:7.4.527

Problem:    Still confusing regexp failure and NFA_TOO_EXPENSIVE.
Solution:   NFA changes equivalent of 7.4.526.

https://code.google.com/p/vim/source/detail?r=v7-4-527
Merge pull request #1735 from fwalch/vim-7.4.527

vim-patch:7.4.527