[fix] jump to a line contains regex escape charactors may failed

[hbuexinxin]

if tag contains regex charactors (such as / - $ etc), may matchstrpos maybe failed.

if tag is [4-2] , matchstrpos will throw error blow:

Error detected while processing function vista#cursor#FoldOrJump[9]..vista#jump#TagLine:                                                                                              
line   16:
E944: Reverse range in character class

[liuchengxu]

Thank you!