[RFC] Cleanup user documentation build

This PR does some cleanup in the Makefile of the user documentation.
The first commit makes `make html` work.
Also some generated files got deleted and the `*.1` files are converted to UTF-8.
I'm getting this on OS X 10.9.4:
```
% file manpages/ja/vim-ja.man
manpages/ja/vim-ja.man: ERROR: line 22: regexec error 17, (illegal byte sequence)
```
and
```
% head manpages/ja/vim-ja.man 
VIM(1)                                                                  VIM(1)



åå
       vim − Vi IMproved, ããã°ã©ãã®ããã¹ãã¨ãã£ã¿

æ¸å¼
       vim [options] [file ..]
       vim [options] −

```
full output: https://gist.github.com/stefan991/d84fa2196951a7c1312d