Release coccinelle-0.2.4rc4

** Language:
- scripts now have names and can declare metavariables that are seen by
  SmPL as identifier metavariables, see demos/{python,ocaml}tococci.cocci
- declaration (match variable declarations) and field (match structure
  field declarations) metavariables
- matching of array initializations and of enum declarations

** Features:
- compatability with Python 2.7.  Thanks to Richard W.M. Jones for pointing
  out the problem
- python and ocaml string representations of parameter lists and expression
  lists
- try simpler patterns on glimpse failure
- graceful and immediate failure when a virtual rule is defined on the
  command line, but not in the rule
- spatch returns -1 when a virtual rule is requested that is not supported
- no transformation when using * with the option -no_show_diff
- expanded +++ file name for match output
- struct *^* and enum *^* metavariable types

** Bugfix:
- detect used after metavariables in simple statement metavariable match
- allow inheriting position variables over rules that make transformations
  but depend on virtual rules that are not defined on the command line
- treat top-level tokens in decl visitor.  Thanks to Peter Tummeltshammer
  for noticing a resulting problem.
- improve typing of the result of an assignment expression
- eliminate some recursive calls in C code parsing to avoid stack overflows
- better pretty printing of #define when the whole line is removed
- better pretty printing of asm code containing
  "::[input]"r"(&coherence_data[i])"
- allow pretty printing of C code with nameless bit fields
- avoid adding an error message to standard output if ocamlfind is not
  found
- struct/union/enum-typed metavariables with a metavariable type name