libmd: stop exporting _block symbols

These are needed across compilation units so we can keep the _libmd_
prefixing bits (though I suspect we're not likely to collide), but we
don't need to be exporting the unprefixed versions of these; it's an
implementation detail.

PR:		280784 (exp-run)
Reviewed by:	delphij, fuz
Differential Revision:	https://reviews.freebsd.org/D34498

lib/libmd/rmd160c.c

@@ -544,6 +544,4 @@ __weak_reference(_libmd_RIPEMD160_Final, RIPEMD160_Final);
 __weak_reference(_libmd_RIPEMD160_Transform, RIPEMD160_Transform);
 #undef RMD160_version
 __weak_reference(_libmd_RMD160_version, RMD160_version);
-#undef ripemd160_block
-__weak_reference(_libmd_ripemd160_block, ripemd160_block);
 #endif

lib/libmd/sha1c.c

@@ -487,8 +487,6 @@ __weak_reference(_libmd_SHA_Final, SHA_Final);
 __weak_reference(_libmd_SHA_Transform, SHA_Transform);
 #undef SHA_version
 __weak_reference(_libmd_SHA_version, SHA_version);
-#undef sha_block
-__weak_reference(_libmd_sha_block, sha_block);
 #undef SHA1_Init
 __weak_reference(_libmd_SHA1_Init, SHA1_Init);
 #undef SHA1_Update
@@ -499,6 +497,4 @@ __weak_reference(_libmd_SHA1_Final, SHA1_Final);
 __weak_reference(_libmd_SHA1_Transform, SHA1_Transform);
 #undef SHA1_version
 __weak_reference(_libmd_SHA1_version, SHA1_version);
-#undef sha1_block
-__weak_reference(_libmd_sha1_block, sha1_block);
 #endif