Fork channel

Create a new channel as a copy of main.

Rename channel

Rename main to:

Delete channel

Delete main? This cannot be undone.

fixup-cpu-mode.s
// RUN: llvm-mc -filetype=obj -triple x86_64-pc-linux-gnu %s -o %t
// RUN: llvm-objdump -d %t | FileCheck %s

//PR18303
.global edata
sub $edata, %r12 // CHECK: subq $0, %r12
.code32