* lib/af_alg.h: Test HAVE_* macro through '#if', not '#ifdef'.
* lib/af_alg.c: Include "af_alg.h" before the other header files.
* lib/md5.c: Include "af_alg.h" unconditionally.
(md5_stream): Invoke afalg_stream unconditionally.
* lib/sha1.c: Include "af_alg.h" unconditionally.
(sha1_stream): Invoke afalg_stream unconditionally.
* lib/sha256.c: Include "af_alg.h" unconditionally.
(sha256_stream, sha224_stream): Invoke afalg_stream unconditionally.
* lib/sha512.c: Include "af_alg.h" unconditionally.
(sha512_stream, sha384_stream): Invoke afalg_stream unconditionally.
* m4/af_alg.m4: Renamed from m4/linux-if-alg.m4.
(gl_AF_ALG): Renamed from gl_LINUX_IF_ALG_H.
* modules/crypto/af_alg: New file.
* modules/crypto/md5 (Files): Remove files that are now in the
'crypto/af_alg' module.
(Depends-on): Add crypto/af_alg.
(configure.ac): Remove gl_LINUX_IF_ALG_H invocation.
(Makefile.am): Don't mention af_alg.c here.
* modules/crypto/sha1 (Files): Remove files that are now in the
'crypto/af_alg' module.
(Depends-on): Add crypto/af_alg.
(configure.ac): Remove gl_LINUX_IF_ALG_H invocation.
(Makefile.am): Don't mention af_alg.c here.
* modules/crypto/sha256 (Files): Remove files that are now in the
'crypto/af_alg' module.
(Depends-on): Add crypto/af_alg.
(configure.ac): Remove gl_LINUX_IF_ALG_H invocation.
(Makefile.am): Don't mention af_alg.c here.
* modules/crypto/sha512 (Files): Remove files that are now in the
'crypto/af_alg' module.
(Depends-on): Add crypto/af_alg.
(configure.ac): Remove gl_LINUX_IF_ALG_H invocation.
(Makefile.am): Don't mention af_alg.c here.