RFC: https://wiki.php.net/rfc/saner-numeric-strings
This removes the -1 allow_error mode from is_numeric_string functions and replaces it by
a trailing boolean out argument to preserve BC in a couple of places.
Most of the changes can be resumed to "numeric" strings which emitted a E_NOTICE now emit
a E_WARNING and "numeric" strings which emitted a E_WARNING now throw a TypeError.
This mostly affects:
- String offsets
- Arithmetic operations
- Bitwise operations
Closes GH-5762
I'm removing the argument entirely here, but we might want to change
this to passing null or and empty array instead, if the impact of
dropping it entirely turns out to be too large.
This was deprecated as part of https://wiki.php.net/rfc/deprecations_php_7_2
as a doc-only deprecation.
