First steps at command documentation: C compilers and linkers.

Each command gets a doc.go file for godoc to analyze. Its main
element is a package comment.

R=rsc
CC=go-dev
http://go/go-review/1018029

src/cmd/5c/doc.go

+// 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.
+
+/*
+
+5c is a version of the Plan 9 C compiler documented at
+
+	http://plan9.bell-labs.com/magic/man2html/1/2c
+
+Its target architecture is the ARM, referred to by these tools as arm.
+
+*/
+package documentation

src/cmd/5l/doc.go

+// 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.
+
+/*
+
+5l is a modified version of the Plan 9 loader documented at
+
+	http://plan9.bell-labs.com/magic/man2html/1/2l
+
+Its target architecture is the ARM, referred to by these tools as arm.
+
+Major changes include:
+	- support for segmented stacks (this feature is implemented here, not in the compilers).
+
+
+Original options are listed in the link above.
+
+Options new in this version:
+-L dir1,dir2,..
+	Search for libraries (package files) in the comma-separated list of directories.
+	The default is the single location $GOROOT/pkg/$GOOS_arm.
+
+
+*/
+package documentation

src/cmd/6c/doc.go

+// 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.
+
+/*
+
+6c is a version of the Plan 9 C compiler documented at
+
+	http://plan9.bell-labs.com/magic/man2html/1/2c
+
+Its target architecture is the x86-64, referred to by these tools as amd64.
+
+*/
+package documentation

src/cmd/6l/doc.go

+// 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.
+
+/*
+
+6l is a modified version of the Plan 9 loader documented at
+
+	http://plan9.bell-labs.com/magic/man2html/1/2l
+
+Its target architecture is the x86-64, referred to by these tools as amd64.
+
+Major changes include:
+	- support for ELF and Mach-O binary files 
+	- support for segmented stacks (this feature is implemented here, not in the compilers).
+
+
+Original options are listed in the link above.
+
+Options new in this version:
+
+-H6
+	Write Apple Mach-O binaries (default when $GOOS is darwin)
+-H7
+	Write Linux ELF binaries (default when $GOOS is linux)
+-L dir1,dir2,..
+	Search for libraries (package files) in the comma-separated list of directories.
+	The default is the single location $GOROOT/pkg/$GOOS_amd64.
+
+
+*/
+package documentation

src/cmd/8c/doc.go

+// 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.
+
+/*
+
+8c is a version of the Plan 9 C compiler documented at
+
+	http://plan9.bell-labs.com/magic/man2html/1/2c
+
+Its target architecture is the x86, referred to by these tools for historical reasons as 386.
+
+*/
+package documentation

src/cmd/8l/doc.go

+// 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.
+
+/*
+
+8l is a modified version of the Plan 9 loader documented at
+
+	http://plan9.bell-labs.com/magic/man2html/1/2l
+
+Its target architecture is the x86, referred to by these tools for historical reasons as 386.
+
+Major changes include:
+	- support for ELF and Mach-O binary files 
+	- support for segmented stacks (this feature is implemented here, not in the compilers).
+
+
+Original options are listed in the link above.
+
+Options new in this version:
+
+-H6
+	Write Apple Mach-O binaries (default when $GOOS is darwin)
+-H7
+	Write Linux ELF binaries (default when $GOOS is linux)
+-L dir1,dir2,..
+	Search for libraries (package files) in the comma-separated list of directories.
+	The default is the single location $GOROOT/pkg/$GOOS_386.
+
+
+*/
+package documentation