Use lua generator in place of ex_cmds_defs header trick

Closes #788
Fixes #379
Ref #549
Add const qualifier and explicit length
Fix problem with test47: addition is not bitwise OR

:diffsplit command used to include some flag value twice. If I was using bitwise
OR it would be OK, but I had addition here. Changed to use bitwise OR.
Extend documentation
Merge pull request #840 from ZyX-I/generate-ex_cmds

Use lua generator in place of ex_cmds_defs header trick
vim-patch:7.4.296

Problem:    Can't run tests on Solaris.
Solution:   Change the way VIMRUNTIME is set. (Laurent Blume)

https://code.google.com/p/vim/source/detail?r=v7-4-296
vim-patch:7.4.339

Problem:    Local function is available globally.
Solution:   Add "static".

https://code.google.com/p/vim/source/detail?r=v7-4-339
Merge pull request #1100 from atwupack/vp-7.4.296

vim-patch:7.4.296
Merge pull request #1101 from atwupack/vp-7.4.339

vim-patch:7.4.339
Mark patches 176, 185 and 189 as NA
Merge pull request #1103 from Hinidu/na-patches

Mark patches 176, 185 and 189 as NA
Set the policy to 'OLD' to avoid warning CMP0026 in CMake 3.0.
Merge #954 'Fix the policy warning CMP0026 in CMake 3.0.'
CMake: Generate helptags during install step.

Fix #1056.
Merge #1106 'CMake: Generate helptags during install step.'
CMake: Use DESTDIR for helptags generation.
Merge #1110 'CMake: Use DESTDIR for helptags generation.'
Remove third argument of concat_fnames().

Running `$ ag concat_fnames` reveals that the third argument is `true`,
except for one instance where vim_strcat() can be used instead.
document concat_fnames()