require -z for importer

I thought running all the bad tests would be useful, but it turns out I've never done that. Lets just require you to have a zend checkout

Reviewed By: @scannell

Differential Revision: D988254
make use ($this) an error

matching zend. I killed all the uses of it in www and right before this pushes, I'll kill whatever is left on the wednesday.

Reviewed By: @paroski

Differential Revision: D804982
Fixed incompatibility of str_replace with Zend

Fixed incompatibility of str_replace with Zend

Closes #1106

Reviewed By: @ptarjan

Differential Revision: D989582

Pulled By: @scannell
Increase iterations of some vm-perf benchmarks

big and nbody both have a substantial amount of time spent in
the JIT.  Increase the iteration count to focus on generated code
perf.

Reviewed By: @ottoni

Differential Revision: D990726
SPL autoload handlers should use context of registration

SPL autoload functions need to capture the context in which they are registered and be called in that context. This comes up when a class method is registered as an autoload handler that is private and/or calls private methods -- the accessibility checks fail without using the proper context. Thus, save off a CufIter and use that to invoke the function instead of just a function object. This fixes a Zend test as well.

Closes #1020

Reviewed By: @markw65

Differential Revision: D976387
mkdir to return false when path already exists

mkdir should return false if the path already exists to match
Zend

Closes #1113
Closes #1114

Reviewed By: @JoelMarcey

Differential Revision: D990897

Pulled By: @scannell