Thrift: Fix thrift.vim.

Thrift: Fix thrift.vim.

Summary:
thrift.vim has not been deleting its HiLink command.
This causes you to get a (recoverable) error every time you
open a C++ or PHP file after opening a thrift file.
This change deletes the HiLink command, preventing this error.

Reviewed By: martin

Test Plan:
Opened a thrift file, then opened a C++ file in the same session.
Both were highlighted properly.

Revert Plan: ok

git-svn-id: https://svn.apache.org/repos/asf/incubator/thrift/trunk@665194 13f79535-47bb-0310-9956-ffa450edef68