attach injection on Linux

_From [derek.br...@gmail.com](https://code.google.com/u/117968039472581148324/) on February 24, 2009 10:01:18_

this was PR 204490

focusing on Linux as Windows has issues that are best solved with a kernel
driver, unless we think we can rely on backward decoding heuristics or
don't mind losing control for a while

we do have some issues on Linux:
- ability to suspend threads before we have control of them: we will
probably rely on ptrace (xref issue #37 )
- determining the state of sharing of CLONE_\* among threads: should
probably use a modify-and-observe approach

_Original issue: http://code.google.com/p/dynamorio/issues/detail?id=38_