Document poll(2) logic changes.

See #1206, #1213

README.md

@@ -23,6 +23,17 @@ Redis version >= 1.2.0.
 The library comes with multiple APIs. There is the
 *synchronous API*, the *asynchronous API* and the *reply parsing API*.
 
+## Upgrading to > 1.2.0 (**PRERELEASE**)
+
+* After v1.2.0 we modified how we invoke `poll(2)` to wait for connections to complete, such that we will now retry
+  the call if it is interrupted by a signal until:
+
+  a) The connection succeeds or fails.  
+  b) The overall connection timeout is reached.
+
+  In previous versions, an interrupted `poll(2)` call would cause the connection to fail 
+  with `c->err` set to `REDIS_ERR_IO` and `c->errstr` set to `poll(2): Interrupted system call`.  
+
 ## Upgrading to `1.1.0`
 
 Almost all users will simply need to recompile their applications against the newer version of hiredis.