Read v:count before it is overwritten

[hugomg]

Fixes #42.

The v:count parameter is overwritten whenever we invoke a normal-mode command so we must ensure that we read the value of v:count at the start of our functions, before we call any normal-mode commands.

Another change in this commit is that the computations that use v:count now use it as a multiplier, instead of adding it to the computed distance. The behavior should be the same as before for MoveLineDown(1) but it is different for larger steps such as MoveLineHalfPageDown(). In the previous version, moving half a page twice would only move it half a page + 2 lines.

[matze]

Thanks for further investigating the issue. Could you update the commit message to refer to the correct issue number so the issue will be closed automatically?

[hugomg]

Oops! Looks like I wrote 52 instead of 42 😅. I think it should be working now.

[matze]

Thanks!