Harmonize "#=>" in examples. [ruby-core:30206]

* bignum.c: ditto

* class.c: ditto

* compar.c: ditto

* cont.c: ditto

* dir.c: ditto

* encoding.c: ditto

* enum.c: ditto

* enumerator.c: ditto

* error.c: ditto

* eval.c: ditto

* file.c: ditto

* gc.c: ditto

* io.c: ditto

* load.c: ditto

* marshal.c: ditto

* math.c: ditto

* numeric.c: ditto

* object.c: ditto

* pack.c: ditto

* proc.c: ditto

* process.c: ditto

* random.c: ditto

* range.c: ditto

* re.c: ditto

* ruby.c: ditto

* signal.c: ditto

* sprintf.c: ditto

* string.c: ditto

* struct.c: ditto

* thread.c: ditto

* time.c: ditto

* transcode.c: ditto

* variable.c: ditto

* vm_eval.c: ditto

* vm_method.c: ditto

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@27865 b2dd03c8-39d4-4d8f-98ff-823fe69b080e