Version 1.0 of the Checked C specification

Create Version 1.0 of the Checked C specification now that the design of the Checked C extension is complete.

• Make sure the specification matches what is in the compiler. An exception is flow-sensitive bounds declarations, which are still under development in the compiler. The specification clearly marks all other future work.
• Reorganize the specification so that it is easier to read.
  -- Put all the chapters that describe the language extension first and move the fairly technical chapters on checking bounds declarations to the end of the specification.
  -- Move the related work chapter and the rejected design choices chapter to the appendix. These are informational in nature, not normative, and do not need to be included in the body of the specification.