Fix as many raw type uses as possible

Two couldn't be solved, though; and the others are in deprecated classes.
Remove references to o.p.c.Preconditions, part 1

There are soo many in the code that it's not even funny.

But it has to be done since this class is marked as deprecated.
More Preconditions migrations

And fix a compile error.
Get rid of all checkArgNotNull()

*phew*
Get rid of o.p.c.Preconditions, part 2 and end

Except for deprecated classes and methods.
Optimize imports
BaseParser: move all deprecated rules in their own "section" of the file
BaseParser: add all rules (except one) of RFC 5234, appendix B, section 1

The excluded rule is LWSP. The RFC does not even recommend it, so...
Optimize Javadoc imports
Use Set's .add() return code

In many places a .contains() test was done before attempting to .add(); which is
not needed.

Simplifies the code in quite a few places.
Reformat Filters

Make parameters final, all under 80 columns etc etc.
Cleanup of org.parboiled.matchervisitors.*
Cleanup of org.parboiled.buffers

In particular, make the documentation _not_ lie: buffers were not immutable!

Now they are (except for MutableInputBuffer, but this one is, uh, special. Is it
useful at all?).
ArrayBuilder: is unused, mark as deprecated, schedule for removal
InstructionGroupPreparer: make inner class MD5Digest immutable
Get rid of the dependency on Base64

And add a comment. We must REALLY get rid of .toString() based tests!
InstructionGroupPreparer, part 1

More to do...
InstructionGroupPreparer, part 2

More to do...

My god this code sucks...
InstructionGroupPreparer, part 3

More to do!
InstructionGroupPreparer, final part for now

But a real tester needs to be written for bytecode tests. String dumps? Meh.