Copy stable/9 to releng/9.3 as part of the 9.3-RELEASE cycle.Approved by: re (implicit)Sponsored by: The FreeBSD Foundation
MFC r237410: zlib 1.2.7.
MFV: Update zlib to 1.2.7.(x86 assembler optimization disabled for now because itrequires the new .cfi_* directives that is not supportedby base system binutils).MFC after: 1 week
Vendor import of zlib 1.2.6.