MFC r258903,r264487,r271699,r288415:

MFC r258903,r264487,r271699,r288415:

r258903 (by markj):

Enable some previously-disabled DTrace tests for umod, ufunc and usym. They
expect the installed ksh binary to be named "ksh", which is not the case
when it's installed on FreeBSD via the shells/ksh93 port. Allow for it to be
"ksh93" as well so that the tests can actually pass.

r264487 (by markj):

Replace a few Solarisisms with their corresponding FreeBSDisms to make a few
printf tests pass.

r271699 (by markj):

Implement a workaround to allow this test program to be compiled with clang.
It seems that if a pragma is used to define a weak alias for a local
function, the pragma must appear after the function is defined.

PR:		193056

r288415 (by markj):

MFV r288408:
6266 harden dtrace_difo_chunksize() with respect to malicious DIF

illumos/illumos-gate@395c7a3dcfc66b8b671dc4b3c4a2f0ca26449922

Author: Bryan Cantrill <bryan@joyent.com>

git-svn-id: svn://svn.freebsd.org/base/stable/10@313486 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f