Add more lint checks for style

[brson]

We have one now that checks for camel case on types, variants and traits.

We have some other rules:

• consts are all caps Uppercase statics lint #7523
• every other ident is lower case and underscores

Let's have lint passes for those as well.

[nikomatsakis]

I put this on as a 1.0 milestone because I think that having such lint checks enabled (to warn, probably) by default is something we really ought to have before we release. Specifically I am thinking of warning if variant names are lowercase or variable names are upper case---capitalization rules on types I think are less important.

[graydon]

oops, closed by accident (wrong bug)

[pnkfelix]

Visiting for bug triage, 2013 june 26.

I guess this bug is really a meta-bug, collecting lint additions that the rust dev team wants in as rules for the rustc and standard library code base before 1.0 is released.

There is still at least issue #4639 to resolve, so I'm leaving this open. (Once #4639 is resolved, then I'm guessing we'll close and reopen it as necessary to track whether lint items remain to do.)

[emberian]

Visiting for triage; nothing to add.

[brson]

Still want more of these. Any ideas?

[pnkfelix]

accepted for P-low

[pnkfelix]

tagging as a good mentorship bug, with @brson as the mentor.

[huonw]

Some more ideas:

• Generic type parameters should be camel case, lifetimes should be snake case. (Although people rarely go beyond a single letter for either.)
• modules should be snake case
• no outer parens on if and match conditions