notepad: We pass OFN_FILEMUSTEXIST | OFN_PATHMUSTEXIST to GetOpenFileName, so there is no point in testing file existence.

server: Fix the crashed process exit code when the debugger exits without detaching. Add a conformance test.

winedbg: 'winedbg --auto' and 'winedbg --minidump' should detach when done so as to not mess up the crashed process exit code.