[vim] look for tags in some default dir

Otherwise you neede to relaunch vim so autotags see them

.vim/plugin/cscope_plus.vim

@@ -40,6 +40,11 @@ if has("cscope")
 	    map <M-F8> :CtagsKernelBuild<CR><CR>
 	endif
 
+	set tags+=./tags	" in file directory
+	set tags+=tags		" in current directory
+	"for when programming in build dir
+	set tags+=../tags
+
 	function! GetLocalCscopeDb(pathname)
 		if !isdirectory(a:pathname) ||  a:pathname == $HOME || a:pathname == '/'
 			return