Ph7

How unbounded input size denial-of-service happens in C lexer functions and how to fix it

A high-severity denial-of-service vulnerability was discovered in the PH7 lexer where the `PH7_TokenizePHP()` function accepted arbitrarily large input sizes without validation. An attacker could submit gigabyte-scale PHP code, causing proportional CPU and memory exhaustion. The fix introduces a configurable input size cap enforced before lexer processing begins.