The Great LLVM Tool Renaming

Howdy, oh LLVMers!

As you may or may not have noticed, the LLVM tool `as' has a problematic
name that conflicts with the standard system assembler. This poses a
problem for programs such as `gcc' which searches the path for a
suitable assembler -- it may find the LLVM assembler instead of the
native version, causing compilation errors.

Thus, I am undertaking the project of renaming LLVM tools to have the
`llvm-' prefix. Initially, this will affect `as' and will extend to
`dis', the disassembler.

What will happen is as follows:

* as -> llvm-as
* dis -> llvm-dis

I am making a COPY of the tools/as and tools/dis directories, so a full
build will build a copy of `as' as well as `llvm-as', and same for `dis'
and `llvm-dis'.

This is for compatibility of hard-coded `as' and `dis' in automated
regression tests and elsewhere in documentation, etc. These will be
converted in due time, in the mean time, this is the upgrade path:

* Directories are now copied
* The `obsolete' directories will go away in a week or two, and you will
  be forced to use llvm-as and llvm-dis, but note that this is for your
  benefit! :slight_smile:

If this is unclear or if you have questions/suggestions, we are all