Add Code::blocks project file (cbp) for Chipmunk 7

Add Code::blocks project file (cbp) for Chipmunk 7, and 2 fixes for compilation and usage:
- const for the first data fields in cpCollisionHandler cause compilation
  errors on MinGW, not sure why but just remove const fixes it
- including chipmunk_private.h the second time would cause error because
  it checks if chipmunk.h has been included right in the beginning.
  basically just add a guard ifdef CHIPMUNK_PRIVATE_H_INCLUDED to the
  start of the file to fix