devel/cproto: Update 4.7x => 4.7y

2025/09/01 (4.7y)

• improve manpage discussion of limitations when using cproto's built-in support for C preprocessor directives (Debian #1112126).
• modify makefile for installing manpage to show actual cpp (Debian #1112126).
• improve configure script checks, reducing warnings

PR: 292297