[RFC] vim-patch:7.4.365, 7.4.372, 7.4.373, 7.4.377

**vim-patch:7.4.365**

Problem:    Crash when using ":botright split" when there isn't much space.
Solution:   Add a check for the minimum width/height. (Yukihiro Nakadaira)

https://code.google.com/p/vim/source/detail?r=v7-4-365

I could not recreate the crash mentioned in https://groups.google.com/forum/#!msg/vim_dev/da_8i3UZlT4/OpLPSqIjcsMJ but the calculation of `winheight` is now correct.

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**vim-patch:7.4.372**
Problem:    When 'winminheight' is zero there might not be one line for the current window.
Solution:   Change the size computations. (Yukihiro Nakadaira)

https://code.google.com/p/vim/source/detail?r=v7-4-372

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**vim-patch:7.4.373**

Problem:    Compiler warning for unused argument and unused variable.
Solution:   Add UNUSED.  Move variable inside #ifdef.

https://code.google.com/p/vim/source/detail?r=v7-4-373

I have only applied the changes to `window.c` which changes the scope of two variables.

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**vim-patch:7.4.377**

Problem:    When 'equalalways' is set a split may report "no room" even though there is plenty of room.
Solution:   Compute the available room properly. (Yukihiro Nakadaira)

https://code.google.com/p/vim/source/detail?r=v7-4-377

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Again, there are some more patches for `window.c` to be included here. This will include 7.4.373 which we marked as `NA` but changes the scope of some variables. The others are 7.4.372 and 7.4.377.
:+1: It could cause chaos, but I secretly wish we weren't strict about 80-line limit.