[vala] (11 commits) ...Don't create constant Regex on demand and use static field where possible

[Rico Tzschichholz <ricotz src gnome org>]

Summary of changes:

  7d01cf8... codegen: Drop superfluous dynamic-type cast (*)
  41ad68f... Use more "...".printf to concat strings (*)
  1897979... codegen: Some simplifications (*)
  6fd1e86... vala: Avoid superfluous string copying (*)
  0f65d30... ccode: Replace if-else-tree with switch (*)
  706ff17... Avoid some string copying (*)
  76789fa... vala: Add missing TokeType cases for to_string() (*)
  2d7df5c... field: Drop unused methods (*)
  061d0e1... writer: Some string optimizations (*)
  b552f38... ccodewriter: Use private _bol field instead of property (*)
  e65e411... Don't create constant Regex on demand and use static field  (*)

(*) This commit already existed in another branch; no separate mail sent