MFC r282736: Unbreak build following rev. 282726 (MFC-ed as r314144)

MFC r282726: Ensure libmd symbols do not clash with libcrypto

Add a prefix to all symbols in libmd to avoid incompatibilites
with same-named, but not binary compatible, symbols from libcrypto.

Also introduce Weak aliases to avoid the need to rebuild dependent
binaries and a major version bump.

PR: 199119

Copy head (r256279) to stable/10 as part of the 10.0-RELEASE cycle.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Fix an 11 year old mistake: Let the hash functions take a void* instead
of unsigned char* argument.

Add a new entrypoint to the hashes in libmd:
char *
FooFileChunk(const char *filename, char *buf, off_t offset, off_t length)
Which only hashes part of a file.
Implement FooFile() in terms of this function.

Submitted by: roam

Add Eric Young's RIPEMD160 implementation as well, in case SHA-1
should prove weak. Also fix a few problems with the SHA-1 build.