MFC r307521: libmd: introduce functions that operate on fd instead of filename

MFC r307584

Fix C++ includability of crypto headers with static array sizes

C99 allows array function parameters to use the static keyword for their
sizes. This tells the compiler that the parameter will have at least the
specified size, and calling code will fail to compile if that guarantee is
not met. However, this syntax is not legal in C++.

This commit reverts r300824, which worked around the problem for
sys/sys/md5.h only, and introduces a new macro: min_size(). min_size(x) can
be used in headers as a static array size, but will still compile in C++
mode.

Copy head@r302406 to stable/11 as part of the 11.0-RELEASE cycle.
Prune svn:mergeinfo from the new branch, as nothing has been merged
here.

Additional commits post-branch will follow.

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

libmd: Work around C++'s inability to understand C

Reported by: antoine@ (x265)

Unbreak build following rev. 282726

(Makefile.inc1): add dependency of xinstall on libmd to
avoid failure of parallel bootstrap.

(lib/libmd/*.h): do not redefine symbols if already
defined as macros (libcrypt uses the same sources internally,
redefining symbols with a prefix of its own).

Fixes build failures caused by previous change to libmd.

Reported by: ian
Pointy hat to: thomas

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
Differential Revision: D2216
Reviewed by: roberto, delphij
MFC after: 2 weeks

Just pick up the real thing from <sys/md5.h>

close bin/1648 libmd not 64bit safe.

if something fails to compile now, you need to add #include <sys/types.h>

Partially Submitted by: Jason Thorpe <thorpej@nas.nasa.gov>

Add a structure definition to the MD* Contexts, so that cvs can use
the standard libmd version of MD5 instead of it's own seperate copy..

Change this to do what it should have done from the start.
Add argument for buffer for output.
Fix manuals.

Added "const" to the arguments here and there.

This commit was generated by cvs2svn to compensate for changes in r1802,
which included commits to RCS files with non-trunk default branches.

Reviewed by: phk
Imported libmd. This library contains MD2, MD4 and MD5.
These three boggers pop up all over the place all of the time, so I
decided we needed a library with them. In general they are used for
security checks, so if you use them you want to link them static.