* config.make.in: Add nss-crypt entry.
* crypt/Makefile: If nss-crypt==yes, don't build md5.c, sha256.c,
sha512.c. Don't run md5test, sha256test, sha512test. Pass -DUSE_NSS
and include path for NSS directory to compiler for md5-crypt,
sha256-crypt, sha512-crypt. Link libcrypt.so with -lfreebl3.
* crypt/md5-crypt.c: If USE_NSS is defined, don't use local hash
function implementation, use NSS. Introduce wrappers around the
hash function calls. Little code size optimization.
* crypt/sha256-crypt.c: Likewise.
* crypt/sha512-crypt.c: Likewise.
* scripts/check-local-headers.sh: Ignore nss3 directory.
* configure.in: Rename pic_default to libc_cv_pic_default.
* config.make.in: Likewise.