two new tools
* cache_dump reads out cache entries and prints them in various orders;
  this is the beginning of a more powerful tool that will be used to
  create output for compiler developers to look at
* reduce is a delta debugger that minimizes souper optimizations
Fix souperweb build
Merge pull request #90 from regehr/tools

two new tools
unconditionally build the clang pass with stats enabled -- by default LLVM turns
off stats for a Release build.  my claim is that the cost of stats is
effectively zero and they're often useful so let's just leave them on.