Detect more TeX-related filetypes

[clason]

Now that VimTeX is a full-featured filetype plugin, it would be nice if it triggered for (more) TeX-related filetypes.

Off the top of my head:

1. *.cls: that is recognized by ftplugin.vim, but only if the first line starts with a % (otherwise the filetype is set to st); if you have VimTeX installed, chances are good that your .cls files are LaTeX class files...
2. *.tikz (see Add .tikz file completion for \input #2162)

[lervag]

I believe this may suffice. Please test.

I'm not 100% sure if it is a good idea to override the builtin conditional for cls filetype detection. I don't know and use smalltalk, and so I don't know how likely it is for this change to lead to unexpected behaviour...

[clason]

I believe this may suffice. Please test.

Looks good!

I don't know and use smalltalk, and so I don't know how likely it is for this change to lead to unexpected behaviour...

I don't, either; I guess we'll find out whether the intersection of TeX writers and smalltalk programmers is nonempty...

[lervag]

I don't, either; I guess we'll find out whether the intersection of TeX writers and smalltalk programmers is nonempty...

Hehe, yes; let's take the risk. If there are objections, then I'll probably revert this change. In the meantime, I'll close this issue. :)

[Hans-Guenter]

In my case I see a conflict with Visual Basic class files which also share the extension .cls.

[lervag]

Let's have the discussion at #2226.