Upstreaming an apple local patch by Frederic Riss.

lldb has an expression that runs in the inferior process to collect
the isa values and hash of the class names for classes in the
system's shared cache.  In recent OSes, swift classes are in this
table and the function the jitted expression calls returns demangled
names.  We need to compute the hashes based on the mangled names.
So for these names, return a hash value of 0 which indicates that
lldb should read the class name directly out of the runtime tables
and compute the hash itself.

When this patch is absent, the lldb+swift testsuite has many failures
on a recent macOS system; there isn't a direct non-swift way to
test for this being correct.

<rdar://problem/47935062>

llvm-svn: 359843