tpl: Make the *langURL funcs tace interface{}
tpl: Make the *langURL funcs tace interface{}

Fixes #2447

digitalcraftsman/hugo,mdhender/hugo,mdhender/hugo,gohugoio/hugo,mdhender/hugo,mitchchn/hugo,fedelibre/hugo,MarkDBlackwell/hugo,bogem/hugo,fedelibre/hugo,Zenithar/hugo,jygastaud/hugo,bogem/hugo,mitchchn/hugo,gohugoio/hugo,anthonyfok/hugo,fedelibre/hugo,tubo028/hugo,Zenithar/hugo,fedelibre/hugo,anthonyfok/hugo,jygastaud/hugo,anthonyfok/hugo,MarkDBlackwell/hugo,mayah/hugo,digitalcraftsman/hugo,gohugoio/hugo,mdhender/hugo,mayah/hugo,tubo028/hugo