all: merge dev.typealias into master

For #18130.

f8b41236 [dev.typealias] spec: use term 'embedded field' rather than 'anonymous field'
9ecc3ee2 [dev.typealias] cmd/compile: avoid false positive cycles from type aliases
49b7af8a [dev.typealias] reflect: add test for type aliases
9bbb07dd [dev.typealias] cmd/compile, reflect: fix struct field names for embedded byte, rune
43c70943 [dev.typealias] reflect: fix StructOf use of StructField to match StructField docs
9657e0b0 [dev.typealias] cmd/doc: update for type alias
de2e5459 [dev.typealias] cmd/compile: declare methods after resolving receiver type
9259f307 [dev.typealias] test: match gccgo error messages on alias2.go
5d929167 [dev.typealias] cmd/compile: change Func.Shortname to *Sym
a7c884ef [dev.typealias] go/internal/gccgoimporter: support for type aliases
5802cfd9 [dev.typealias] cmd/compile: export/import test cases for type aliases
d7cabd40 [dev.typealias] go/types: clarified doc string
cc2dcce3 [dev.typealias] cmd/compile: a few better comments related to alias types
5c160b28 [dev.typealias] cmd/compile: improved error message for cyles involving type aliases
b2386dff [dev.typealias] cmd/compile: type-check type alias declarations
ac8421f9 [dev.typealias] cmd/compile: various minor cleanups
f011e0c6 [dev.typealias] cmd/compile, go/types, go/importer: various alias related fixes
49de5f03 [dev.typealias] cmd/compile, go/importer: define export format and implement importing of type aliases
5ceec42d [dev.typealias] go/types: export TypeName.IsAlias so clients can use it
aa1f0681 [dev.typealias] go/types: improved Object printing
c80748e3 [dev.typealias] go/types: remove some more vestiges of prior alias implementation
80d8b69e [dev.typealias] go/types: implement type aliases
a917097b [dev.typealias] go/build: add go1.9 build tag
3e119404 [dev.typealias] cmd/compile: recognize type aliases but complain for now (not yet supported)
e0a05c27 [dev.typealias] cmd/gofmt: added test cases for alias type declarations
2e5116bd [dev.typealias] go/ast, go/parser, go/printer, go/types: initial type alias support

Change-Id: Ia65f2e011fd7195f18e1dce67d4d49b80a261203