Add ~/.tcsh/tcshrc as a (potential) configuration file.

I have quite a long tcshrc file, so I split in in a few files
(~/.tcsh/{settings,aliases,...}.tcsh), this makes it more manageable, but has
the downside that I now have 2 tcsh-related entries in my ~/ directory.

~/.tcshrc & ~/.cshrc are still searched first, and if they exists ~/.tcsh/tcshrc
will not be used; perhaps searching ~/.tcsh/tcshrc before ~/.cshrc is better,
but this is the most 'compatible' way, since nothing changes for users who may
have both files already...

I've also taken the liberty to add a .gitignore in this patch, and I've updated
.cvsignore with a few files that were generated.