[fidl] Compiler implementation for tables

Test: updated existing tests, implemented a table test suite for table edge cases

Change-Id: Id145d12f44544027d0d28c2288ebf5c6de39b446

[fidl] Add a tree visitor to the AST.

This adds a class that lets clients walk the AST, a class
that lets clients walk the AST in declaration order, and
a way of doing testing with .fidl files instead of baking
in raw strings.

Test: Tests added in visitor_unittests.cpp

Change-Id: I5d4824cdb80a8acd8a3cfb8e9cb5586bdeacf365

[fidl] Validate library names.

Bug: FIDL-181
Test: verified that compilation failed for wrongly-formatted library names
Change-Id: Ie15364a2e8dc54ee12748545f2a49dd7a520fb01

[fidl] Calculate max out-of-line payload size

Also write some unit tests for this and for max handle counting.

TEST=implement some fidl compiler tests

Change-Id: I6d6758100d432e0769bf18b0cd57925c9a56d9b8