Allow access to functions in inline assembly.

docs/control-structures.rst

@@ -452,8 +452,8 @@ Note that the order of arguments is reversed in functional-style as opposed to t
 way. If you use functional-style, the first argument will end up on the stack top.
 
 
-Access to External Variables
-----------------------------
+Access to External Variables and Functions
+------------------------------------------
 
 Solidity variables and other identifiers can be accessed by simply using their name.
 For storage and memory variables, this will push the address and not the value onto the
@@ -461,6 +461,17 @@ stack. Also note that non-struct and non-array storage variable addresses occupy
 on the stack: One for the address and one for the byte offset inside the storage slot.
 In assignments (see below), we can even use local Solidity variables to assign to.
 
+Functions external to inline assembly can also be accessed: The assemble will
+push their entry label (with virtual function resolution applied). The calling semantics
+in solidity are:
+
+ - the caller pushes return label, arg1, arg2, ..., argn
+ - the call returns with ret1, ret2, ..., retn
+
+This feature is still a bit cumbersome to use, because the stack offset essentially
+changes during the call, and thus references to local variables will be wrong.
+It is planned that the stack height changes can be specified in inline assembly.
+
 .. code::
 
 	contract c {