configure.in: check dtace -G

	* configure.in (RUBY_DTRACE_POSTPROCESS): check if the object file
  is really modified by `dtrace -G`, this command is very system
  dependent.
	* common.mk (ruby-glommed.o): dependency on $(OBJ) should be written
	  in common.mk (in which OBJ is defined) because of Makefile include
	  and parse order. This partly reverts r49419.
	  [ruby-dev:48849] [Bug #10808]

	* Makefile.in (ruby-glommed.o): ditto.

	* Makefile.in (ruby-glommed.o): remove excess $(DTRACE_OBJ) because
	  it is included in $(OBJS) since r49451.

	* Makefile.in (probes.o): should depend on $(DTRACE_DEPENDENT_OBJS)

	* Makefile.in (probes.stamp): rebuild dtrace dependent objects
	  only when `dtrace -G` modifies its input files.


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_2_2@49686 b2dd03c8-39d4-4d8f-98ff-823fe69b080e