Baby steps toward SystemVerilog support, and other VL enhancements.

Mostly this is focused on VL's lexer.
  - Moved the lexer into a new directory, vl/loader/lexer/*
  - Modernized and cleaned up the lexer code
  - Parameterized keyword and operator handling, and added support
    for all SystemVerilog-2012 keywords and new operators
  - Added high-level lexer configuration to say which edition of
    Verilog you want it to implement
 Todo List:
  - Review the syntax for literal numbers, strings, identifiers,
    etc., and make sure it's correct

Other VL changes:
 - Add edition options to loader, various vl toolkit commands
 - Split expressions out of parsetree.lisp (into expr.lisp)
 - Standardized waterfall-disabling stuff
 - Update documentation in various places to indicate things that are
   Verilog-2005 specific
 - Update warning code, add vl-warninglist-fix

STD/util:
 - Add new defval macro, basically just defconst with xval integration
 - Add defconsts and defval to *std-exports*
 - Start defsum book (very preliminary, not yet usable)

git-svn-id: http://acl2-books.googlecode.com/svn/trunk@2437 303c5b2c-9740-0410-b014-fd8f9db7be32
Making an error message slightly more helpful by adding a prompt for my most common mistake that results in the error.

git-svn-id: http://acl2-books.googlecode.com/svn/trunk@2438 303c5b2c-9740-0410-b014-fd8f9db7be32
fix missing include-book

git-svn-id: http://acl2-books.googlecode.com/svn/trunk@2439 303c5b2c-9740-0410-b014-fd8f9db7be32