stats URL/response code filters did the opposite

- Per Github, URL/code filters, if specified, actually filtered
out only the code/URL as opposed to restricting it to the URL/code of
interest

Closes #912

Differential Revision: D906156
'_' -> '-' in runtime/vm/*

To be consistent with runtime/vm/jit

Differential Revision: D906425
fix compile_string memory leak

Fix memory leak in compile_string

Closes #879
Closes #917

Differential Revision: D908222
Don't pass type prediction after Div interpOne

This is generating CheckTypes even when the value is not used.

Differential Revision: D907386
Implement session_status()

And export PHP_SESSION_(NONE|DISABLED|ACTIVE) constants.

Differential Revision: D908419