Stdlib: urlencode, rawurlencode, parse_url for routing

[PurHur]

Problem

Query strings are parsed in Superglobals, but link generation and routers often need urlencode / parse_url.

Goal

Add minimal URL helpers to ext/standard/.

Tasks

• VM delegate to PHP implementations
• JIT: call libc or embed small encoder
• PHPT: encode query arg, parse REQUEST_URI components
• Use in examples/003-MiniWebApp router

Acceptance criteria

echo '<a href="?name=' . urlencode($name) . '">'; compiles and runs.