Move files from src/ to src/nvim/.
- src/nvim/ becomes the new root dir for nvim executable sources.
- src/libnvim/ is planned to become root dir of the neovim library.

Problem:  Using just "$" does not cause an error message.
Solution: Check for empty environment variable name.
          (Christian Brabandt)

https://code.google.com/p/vim/source/detail?r=00228400629e28384f7f52556c3c119ba0d0a44d

Problem:  Using exists() on a funcref for a script-local function
          does not work.
Solution: Translate <SNR> to the special byte sequence.
          Add a test.

https://code.google.com/p/vim/source/detail?r=1a5ed2626b26a982e307a206572121a557adf709

Problem:    Can't call a global function with "g:" in an expression.
Solution:   Skip the "g:" when looking up the function.

https://code.google.com/p/vim/source/detail?r=8ec9d2196bee0c5108f2d2c196a660a7f4e5f29f

Problem:  Can't define a function starting with "g:". Can't assign a
          funcref to a buffer-local variable.
Solution: Skip "g:" at the start of a function name.
          Don't check for colons when assigning to a variable.

https://code.google.com/p/vim/source/detail?r=00acac0af680c2d8c82db5258474b121a5908926

Problem:  It is possible to define a function with a colon in the name.  It
          is possible to define a function with a lower case character if a
          "#" appears after the name.
Solution: Disallow using a colon other than with "s:".  Ignore "#" after the
          name.

https://code.google.com/p/vim/source/detail?r=6bc874e4789a0f912b4fd6b23afecf19d80b1605