Ruby

[EXPERIMENTAL]

• iseq.c: add following two methods.
• ISeq#line_trace_all returns all line traces (line numbers)
• ISeq#line_trace_specify(pos, set) set `pos'th line event to
  specified_line event (if set is true).
  These features are introduced for debuggers (mainly to make
  breakpoint).
• iseq.h: add decl. of C APIs.
• test/ruby/test_iseq.rb: add tests.
• vm_trace.c: add `specified_line' event.
• include/ruby/ruby.h: ditto.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@38076 b2dd03c8-39d4-4d8f-98ff-823fe69b080e