Cil2Csyntax: added goto and labels; added assignment between structs

Kildall: simplified the interface
Constprop, CSE, Allocation, Linearize: updated for the new Kildall
RTL, LTL: removed the well-formedness condition on the CFG, 
  it is no longer necessary with the new Kildall and it is problematic
  for validated optimizations.
Maps: more efficient implementation of PTree.fold.


git-svn-id: https://yquem.inria.fr/compcert/svn/compcert/trunk@1124 fca1b0fc-160b-0410-b1d3-a4f43f01ea2e