Use "config.h", not <config.h>.

Rev: src/nettle/cbc.c:1.7
Rev: src/nettle/hmac.c:1.5
Rev: src/nettle/knuth-lfib.c:1.3
Rev: src/nettle/md5-compat.c:1.4
Rev: src/nettle/md5-meta.c:1.3
Rev: src/nettle/md5.c:1.7
Rev: src/nettle/memxor.c:1.3
Rev: src/nettle/nettle-internal.c:1.4