remove information about line num
add policy for implementation
add test for jumping across a line.
refactor the process using searchpos()
Merge branch 'across-lines' into dev

Conflicts:
	autoload/clever_f.vim
	test/vspec.vim
set noignorecase for searchpos and restore it after the search.
return empty string when the search fails.
tiny refactoring for a code layout
fix bug which occurs when a target char exists at the head of line.