Suppress -Wstrict-prototypes for several zlib files

Clang 15 is more strict about function definitions not matching
declarations, and zlib has a lot of these, but since it is contributed
code (and in K&R style to boot), suppress those warnings instead.

MFC after: 3 days

(cherry picked from commit e83ffec3af2e71cc64348d58481c87db9efbac92)