doc doc doc

R=r
http://go/go-review/1016039

src/cmd/cgo/doc.go

@@ -0,0 +1,35 @@
+// Copyright 2009 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+/*
+
+Cgo enables the creation of Go packages that call C code.
+
+Usage: cgo [compiler options] file.go
+
+The compiler options are passed through uninterpreted when
+invoking gcc to compile the C parts of the package.
+
+The input file.go is a syntactically valid Go source file that imports
+the pseudo-package "C" and then refers to types such as C.size_t,
+variables such as C.stdout, or functions such as C.putchar.
+
+If the import of "C" is immediately preceded by a comment, that
+comment is used as a header when compiling the C parts of
+the package.  For example:
+
+	// #include <stdio.h>
+	// #include <errno.h>
+	import "C"
+
+Cgo transforms the input file into four output files: two Go source
+files, a C file for 6c (or 8c or 5c), and a C file for gcc.
+
+The standard package makefile rules in Make.pkg automate the
+process of using cgo.  See $GOROOT/misc/cgo/stdio and
+$GOROOT/misc/cgo/gmp for examples.
+
+Cgo does not yet work with gccgo.
+*/
+package documentation