Implement return hooks for Lua functions (zero-cost if disabled).

doc/changes.html

@@ -56,7 +56,7 @@ to see whether newer versions are available.
 <h2 id="snap">Development Snapshot</h2>
 <ul>
 <li>Build of preliminary x64 interpreter works on Linux/x64 or WIN64.</li>
-<li>Implement call hooks (zero-cost if disabled).</li>
+<li>Implement call/return hooks (zero-cost if disabled).</li>
 <li>Major redesign of internal function call handling.</li>
 <li>Implement yield from C hooks.</li>
 <li>Add abstract C call handling to IR.</li>

doc/status.html

@@ -90,8 +90,8 @@ known incompatibilities with standard Lua:
 <ul>
 <li>
 The Lua <b>debug API</b> is missing a couple of features (return
-hooks) and shows slightly different behavior (no per-coroutine hooks,
-no tail call counting).
+hooks for non-Lua functions) and shows slightly different behavior
+(no per-coroutine hooks, no tail call counting).
 </li>
 <li>
 <b>Bytecode</b> currently cannot be loaded or dumped. Note that