Remove uint32_t assignment operator from Status

Summary:
It is not presently used, and it's quite dangerous to use -- it assumes the
integer is an osx kern_return_t, but very few of the integers we have lying
around are mach kernel error codes. The error can still be used to a
mach error using a slightly longer (but more explicit) syntax.

Reviewers: jingham

Subscribers: lldb-commits

Differential Revision: https://reviews.llvm.org/D35305

llvm-svn: 317093