[Windows, Process] Fix an issue in windows thread handling that was causing LLDB to hang

Summary: The function ResumeThread on Windows returns a DWORD which is an unsigned int. In TargetThreadWindows::DoResume, there's code that determines how many times to call ResumeThread based on whether the return value is greater than 0. Since the function returns -1 (as an unsigned int) on failure, this was getting stuck in an infinite loop if ResumeThread failed for any reason. The correct thing to do is check whether the return value is -1 and then return the appropriate error instead of ignoring the return value.

Reviewers: asmith, zturner, labath

Reviewed By: zturner

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D47020

llvm-svn: 332670