components/valgrind: numerous regtest failures with CBE 11.4.81

[paulfloyd]

With Solaris 11.4 CBE 11.4.81 I'm getting many regression test failures.

I looked at a few and they are related to the sys_getsetcontext syscall wrapper.

There are 2 new values for 'flag' that are not handled (CLRSSONSTACK and SETUJMPBUF). Because they aren't handled this assert triggers

default:
VG_(unimplemented)("Syswrap of the context call with flag %ld.", SARG1);
/NOTREACHED/
break;