for casual use.  Usage: (1) assign {} to COVERAGE__, (2) require or
  load Ruby source file, and (3) COVERAGE__["sourcefilepath"] will
  return an array whose elements represent number of executions per
  line of source code.

* vm_core.h: add field of coverage array to iseq.

* iseq.c (prepare_iseq_build): ditto.

* insns.def (trace): update coverage array.

* parse.y (coverage): create and initialize coverage array.

* compile.h (ADD_TRACE): add trace instruction to update covearge
  array.

* thread.c (clear_coverage): delete coverage array when forking.
  Otherwise, double count of coverage may occur.

* lib/coverage.rb: sample coverage measurement tool.

* error.c: distinguish explicitly between parse_in_eval and
  mild_compile_error.

* load.c: ditto.

* vm_eval.c: ditto.


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@17781 b2dd03c8-39d4-4d8f-98ff-823fe69b080e