doc: Fix enums.texi failure on out-of-tree builds

enums.texi is a generated file so we should not look for it in $(srcdir).
When we do, chaos ensues:

    mv -f enums.texi-tmp enums.texi
    mkdir enums
    ../../doc/scripts/split-texi.pl enums enum < ../../doc/enums.texi
    /bin/bash: ../../doc/enums.texi: No such file or directory
    make[4]: *** [stamp_enums] Error 1
    make[4]: Leaving directory `/home/user/gnutls/build/doc'
    make[3]: *** [all-recursive] Error 1
    make[3]: Leaving directory `/home/user/gnutls/build/doc'
    make[2]: *** [all] Error 2
    make[2]: Leaving directory `/home/user/gnutls/build/doc'
    make[1]: *** [all-recursive] Error 1
    make[1]: Leaving directory `/home/user/gnutls/build'
    make: *** [all] Error 2

Signed-off-by: Kevin Cernekee <cernekee@gmail.com>
updated gnulib

This pulls in upstream commit cb3c90598 (stdint, read-file: fix missing
SIZE_MAX on Android).

Signed-off-by: Kevin Cernekee <cernekee@gmail.com>
clang warning fixes
silence some warnings
more clang warning fixes
explicit type conversions when needed
ciphersuites that utilize SHA256 or SHA384 are only available in TLS 1.0

The SSL 3.0 protocol (rfc6101) uses a variant of HMAC that is only
defined for MD5 and SHA1. Thus if such a ciphersuite is negotiated under
SSL 3.0, it will during MAC initialization.
doc update
set correct value if found
updated