add relooper sources

Author: kripken

src/relooper/README.markdown

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+
+Relooper
+========
+
+This is an optimized C++ implemention of the Relooper algorithm originally
+developed as part of Emscripten. This implementation includes optimizations
+added since the original academic paper [1] - see paper.pdf - was published
+about it, and is written in an LLVM-friendly way with the goal of inclusion
+in upstream LLVM.
+
+License: MIT&LLVM
+
+[1] Alon Zakai. 2011. Emscripten: an LLVM-to-JavaScript compiler. In Proceedings of the ACM international conference companion on Object oriented programming systems languages and applications companion (SPLASH '11). ACM, New York, NY, USA, 301-312. DOI=10.1145/2048147.2048224 http://doi.acm.org/10.1145/2048147.2048224
+