Moved stack-internal parts of tcp.h to tcp_impl.h, tcp.h now only contains the actual application programmer's API

CHANGELOG

@@ -5,12 +5,6 @@ FUTURE
     problems with exoteric (/DSP) architectures showing these problems.
     We still have to fix some of these issues neatly.
 
-  * TODO: the PPP code is broken in a few ways. There are namespace
-    collisions on BSD systems and many assumptions on word-length
-    (sizeof(int)). In ppp.c an assumption is made on the availability of
-    a thread subsystem. Either PPP needs to be moved to contrib/ports/???
-    or rearranged to be more generic.
-
 HISTORY
 
 (CVS HEAD)
@@ -19,6 +13,10 @@ HISTORY
 
   ++ New features:
 
+  2010-02-21: Simon Goldschmidt
+  * tcp.h (and usages), added tcp_impl.h: Splitted API and internal
+    implementation of tcp to make API usage cleare to application programmers
+
   2010-02-14: Simon Goldschmidt/Stephane Lesage
   * ip_addr.h: Improved some defines working on ip addresses, added faster
     macro to copy addresses that cannot be NULL