[fidl] Initial formatter implementation.

Test: tests added in formatter_unittest.cc

Change-Id: Iadfb0b891c98b4c865cdc96314ea7bba71ee589c

[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] Add using type aliasing

This CL implements most of FTP-002. You can use use "zx.time" and
"zx.duration". The situation for status is complicated by the fact that
status is currently a keywork in FIDL. You can use the new definition
as "zx.@status". Once we migrate all clients off the "status" keyword
and onto "zx.@status", we can complete FTP-002 by removing the keyword
from the compiler and migrating all clients from "zx.@status" to
"zx.status".

FIDL-253 #comment

Test: spaceship.fidl
Change-Id: I93f508dc95ecc56a3cdbd3fc1c40346d358aeefe

[fidl] Generate declarations for simple C client bindings

The implementations will be in a subsequent CL.

FIDL-162 #comment

Test: Cannot test FIDL compiler in Zircon (FIDL-227)
Change-Id: I63f5ea5b89c663239f55fac57db18ab1e75e9b76

[fidl] Centralize naming of generated things

Change-Id: Id8231aad2cc8603d7c431b3999740534bcbccd7b

[fidl] Tables generator stub

Change-Id: I6faefe1f6df1f22db81cfd070da55b2179cff6f8

[fidl] Move Library under flat_ast

Change-Id: Ia6fe3cc68ccbb1965b0f270d1a6bff4b248a3eea

[build][fidl] Separate the fidl (host) lib from the compiler binary.

TO-732

Change-Id: I02625c25d3cac7bb7316370c47c765e1a66e9a01

[fidl] Rename fidl tool to "fidl2".

This prevents collisions during the transition.

TO-733

Change-Id: Ia3a2a80a6bf5a320fb5f06c19044b3af99c7cd2c

[fidl] Generate JSON intermeidate representation

This JSON IR will be used by the various language backends to create
language-specific bindings.

Change-Id: I9555f43b7f7363a1adfbaf34d0a67eceeeb2a37d

[build] allow host tools to be packaged

Change-Id: Ia69305910e09975bee222209aabdb81a2ba2ddc6

[fidl] Start to C header emission

This also moves ownership of library-shared resources into the
library. This includes data structures for tracking source information
and for name resolution.

Change-Id: I13c205dae445d0253d5ec84ae1ed580c42312300

[fidl] Print out lines containing errors

In particular, this plumbs through the ability to go from a
SourceLocation to a line of source.

Change-Id: Ice342006518dc435a737b9a6b1acb443eeecd1fb

[fidl] Add a notion of SourceLocation, and use it in a bit of error reporting

Change-Id: Ie27a04dcd83d639ca2d4a029773c4d6bdadee1e3

[fidl][host] Tweak the fidl host tool build layout

Many of these files are consumed by a currently disabled Garnet gn
target (it is disabled until a future toolchain roll fixes some
fuzzing support infrastructure), which essentially builds a
fuzzing-oriented version of the compiler.

The current layout is expressed as a BUILD.gn file in Zircon. When we
remove these, in favor of generated manifests, this layout will be
difficult to express. The new one puts everything but main into a
separate directory.

Change-Id: I18ea1807fa5d75a3b2620f3a54d4aac4999e0442

[fidl] Introduce SourceManager for owning source data

With modules, and hence many files, error messages etc. may reference
text from multiple files. SourceManager owns the buffers underlying
all the parsed content in the compiler.

This CL also fixes the buffer creation by using std::string::resize
instead of reserve (which doesn't set the size of the string, but only
allocates backing store).

Change-Id: I1670df111a5257c39e4d1166eb453c9515aa7075

[fidl] Remove prototype visitor scaffolding

Change-Id: Ia6ebc1723fe63447ca3f910c26bb27310ec0592b

[fidl] Add fidl host tool

This is the start of the fidl compiler. It parses fidl
files. Eventually this will be used directly to produce C fidl
bindings, and to emit an AST serialized to JSON for other language
bindings to consume. The first is just started in this CL.

Change-Id: I26b5e3af3e816fff17cba09417bb61c126f38f0a