Log Message:
spin: updated to 6.4.7

Version 6.4.7:
- fixed a bug in the parsing of for (...) statements if
  initialized variable declarations appear in the body of the loop
- optimization in interpreting the swarm option, by avoiding
  unnecessary recompilations, plus other small fixes in the
  generation of parameter values for -k and -w with swarms
- added runtime option -W to suppress recompilation of pan if
  the executable already exists
- fixed bug in printing the value of a random seed at the end of
  a randomized run
- added compilation warning if both -DNP and -DNOCLAIM are used
  (in that case -DNP is assumed to override -DNOCLAIM)
- fixed a bug in the parsing of select (...) statements that could
  cause unwarranted syntax errors when larger ranges are used
- switched to executables for Windows PCs that do not require
  a cygwin installation (using mingw32 and mingw64 bit compilations)