1.fix the edit bug when edit is empty,the insert line function is not working.
2.fix the caret bug for delete line.
3.fix the bug for delete the last line.
Merge remote-tracking branch 'remotes/origin/master'

Conflicts:
	components/rtgui/widgets/edit.c
Merge pull request #55 from nongxiaoming/master

1.fix the edit bug when edit is empty,the insert line function is not wo...