Remove esan.

It hasn't seen active development in years, and it hasn't reached a
state where it was useful.

Remove the code until someone is interested in working on it again.

Differential Revision: https://reviews.llvm.org/D59133

llvm-svn: 355862
GitOrigin-RevId: 885b790f89b6068ec4caad8eaa51aa8098327059
49 files changed