TS-1953: remove check_ts_version() from examples

remove the boilerplate check_ts_version() function call from all
examples. This function is nice in a specific example, but it does not
make sense to have it in every single example plugin.

Since the code is compiled, in most cases that's too late to catch
issues with API versions, so it doesn't make sense to begin with.
In order to enable Plugin Developers to do such checks, and #ifdef
around API issues, we'd have to expose the TS_VERSION_* contants.

n.b.: We might want add one example which shows off how to use the
TSTrafficServerGetVersion() API, but we have that in the man page now
anyway.
TS-1953: Remove check_ts_version() from experimental plugins

more axing: This time around, plugins/experimental.
i'm noticing that we do expose TS_VERSION, so ignore most of my last
commit message ;)
TS-1953: remove version check from stable plugins

we're closing the night with a cleanup in the stable plugins.
Thanks, You've been a great crowd.
add some standard extensions to ignore list