FBSD: Handle malloc/free changes in FBSD 12
FreeBSD 12 (r328417) removed the deprecated compatibility macros
MALLOC and FREE. Convert our users to just use the normal malloc and
free, so we can build.
FreeBSD 12 (r334545) also changed malloc() into a macro, which breaks
our own malloc macro in our hcrypto config.h. To fix this, just undef
malloc, if it's already a macro.
Change-Id: I5c683e3834710a60cc78476cbaa7203218b11fe0
Reviewed-on: https://gerrit.openafs.org/13856
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Benjamin Kaduk <kaduk@mit.edu>