PR #634, PR #635, and PR #636 introduced new features that broke
compatibility with older version of Vim. This modifies those changes to
ensure compatibility. Closes#781.
Removes usage of funcref(), closure. Fixes filter() call.
Made globpath calls not use the list argument.
Unlet a variable that is reused (sticky type checking)
v7.4.1989 modified filter() to accept a Funcref
v7.4.2120 Added function "closure" argument
v7.4.2137 add funcref()