Fix determination of lineStart when parsing from middle of file
Fix determination of lineStart when parsing from middle of file

Closes #453

mathiasbynens/acorn,Rich-Harris/acorn,ternjs/acorn,mysticatea/acorn,ternjs/acorn,TimothyGu/acorn,marijnh/acorn,MarcelGerber/acorn,mysticatea/acorn,mysticatea/acorn,ajaxorg/acorn,mathiasbynens/acorn,MarcelGerber/acorn,TimothyGu/acorn,marijnh/acorn,ajaxorg/acorn,Rich-Harris/acorn,Rich-Harris/acorn,mathiasbynens/acorn,TimothyGu/acorn,ajaxorg/acorn,ternjs/acorn,marijnh/acorn,MarcelGerber/acorn