Problem: filetype: openCL files are not recognized
Solution: detect '*.cl' files as opencl or lisp filetype,
include a opencl syntax and filetype plugin (Wu, Zhenyu)
closes: #15825
Signed-off-by: Wu, Zhenyu <wuzhenyu@ustc.edu>
Signed-off-by: Christian Brabandt <cb@256bit.org>
