Description:
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According to Gopal in this insightful blog post 6 years ago:
http://notmysock.org/blog/php/demystifying-autofilter.html

I will borrow the terms used in the above post:
- static - opcodes have been replaced with NOOPs
- dymamic - no opcodes have been replaced

When dynamic inheritance is detected, the following should happen:
- Any cached opcodes for that file become invalid
- We will always recompile the file thereafter

The current behaviour seems to be:
- Any cached opcodes will still be valid (and used as long as on that page request, dynamic inheritance is not detected i.e. the parent class is already known by zend and thus the NOOP makes sense)
- Only if dynamic inheritance is detected, will a recompile happen.

Other than the discrepancy in behaviour between the blog and code, it seems strange that we opt to cache the static version which is not always usable and recompile the dynamic version which is always usable. Furthermore, I'm not sure why we should not cache the dynamic version and use it thereafter.

This patch changes the behaviour to:
- Static opcodes will be cached and used until dynamic inheritance is detected
- When dynamic inheritance is detected, the dynamic opcodes are cached instead
- Thereafter, every request for the file (regardless of whether we can use a static or dynamic version) will always get the cached dynamic version.