Added README.md for PL/0...

Author: yhirose

pl0/README.md

@@ -0,0 +1,21 @@
+PL/0 language example
+=====================
+
+  https://en.wikipedia.org/wiki/PL/0
+
+  * PL/0 PEG syntax
+  * AST generation with symbol scope
+  * Interpreter (slow...)
+  * LLVM Code generation
+  * LLVM JIT execution (fast!)
+
+Usage
+-----
+
+```
+pl0 PATH [--ast] [--llvm] [--jit]
+
+  --ast: Show AST tree
+  --llvm: Dump LLVM IR
+  --jit: LLVM JIT execution
+```