Moving these files from Code/PreSelection to here.

Original logs for PreSelection.cpp:

  revision 1.2
  date: 2002/09/17 23:50:32;  author: lattner;  state: Exp;  lines: +1 -3
  Don't put default parameter values into .cpp files, it breaks 3.x compilers

  revision 1.1
  date: 2002/09/16 15:31:13;  author: vadve;  state: Exp;
  New preselection pass that specializes LLVM code for a target machine,
  while remaining in legal portable LLVM form and preserving type
  information and type safety.

llvm-svn: 3838