LLDB doesn't use this packet so we never hit this, but it looks like
some other projects talk to debugserver and are hitting an assert
(https://github.com/derekparker/delve/issues/1015).
We had an off by 1 in the accounting of the FPU structure sizes.
I added a test that basically just check that 'g' doesn't return
an error (currently it assert in debug builds). I didn't make
it an lldb-server test because it looks like lldb-server doesn't
implement the g packet.
llvm-svn: 331004
