- Preliminary draft of what might become a real spec

- All text taken from go_lang.txt (which is unchanged),
but added a contents section, and sorted the contents
section in a hopefully sensible manner to give it more
structure
- Reordered text to match order of contents section,
did not adjust the language (needs to be done),
but removed sections that were dulicates or invalid

High-level organization of the doc:
- Introduction
- Notation
- Source code representation
- Vocabulary
- Declarations and scope rules
- Types
- Expressions
- Statements
- Function declarations
- Packages
- Program initialization and execution

I hope this new structure will make it much clearer which
pieces are missing and where they need to go. go_lang.txt
has grown somewhat unstructured and new text was added as
we saw fit.

R=r
DELTA=2577  (2577 added, 0 deleted, 0 changed)
OCL=14639
CL=14639