Use non-negative error constants in overlay_exe.h.

The Win32 ExitProcess() API takes an UINT, and we
used to pass negative values to it.

Obviously, those negative values can be represented
just fine in an unsigned integer, but for the sake
of following the API and to avoid future confusion
this commit changes the error constants used by
the overlay helper program to be non-negative.

overlay/overlay_exe/overlay_exe.h

@@ -42,49 +42,49 @@ const wchar_t *MUMBLE_OVERLAY_DLL_NAME = L"mumble_ol_x64.dll";
 enum OverlayHelperError {
 	/// The overlay helper process was not passed any
 	/// arguments.
-	OVERLAY_HELPER_ERROR_EXE_NO_ARGUMENTS            = -1,
+	OVERLAY_HELPER_ERROR_EXE_NO_ARGUMENTS            = 0x0F000001,
 	/// The magic number on the command line of the overlay
 	/// helper process could not be converted to an integer.
-	OVERLAY_HELPER_ERROR_EXE_INVALID_MAGIC_ARGUMENT  = -2,
+	OVERLAY_HELPER_ERROR_EXE_INVALID_MAGIC_ARGUMENT  = 0x0F000002,
 	/// The magic number on the command line of the overlay
 	/// helper did not match the built-in magic number of
 	/// the helper process.
-	OVERLAY_HELPER_ERROR_EXE_MAGIC_MISMATCH          = -3,
+	OVERLAY_HELPER_ERROR_EXE_MAGIC_MISMATCH          = 0x0F000003,
 	/// The overlay helper process was unable to configure
 	/// its environment in preparation of loading the
 	/// overlay DLL.
-	OVERLAY_HELPER_ERROR_EXE_CONFIGURE_ENVIRONMENT   = -4,
+	OVERLAY_HELPER_ERROR_EXE_CONFIGURE_ENVIRONMENT   = 0x0F000004,
 	/// The overlay helper process was unable to get the
 	/// path to the overlay DLL.
-	OVERLAY_HELPER_ERROR_EXE_GET_DLL_PATH            = -5,
+	OVERLAY_HELPER_ERROR_EXE_GET_DLL_PATH            = 0x0F000005,
 	/// The overlay helper process was unable to load the
 	/// overlay DLL.
-	OVERLAY_HELPER_ERROR_EXE_LOAD_DLL                = -6,
+	OVERLAY_HELPER_ERROR_EXE_LOAD_DLL                = 0x0F000006,
 	/// The overlay helper process was uanble to look up
 	/// the 'OverlayHelperProcessMain' entry point in the
 	/// overlay DLL.
-	OVERLAY_HELPER_ERROR_EXE_LOOKUP_ENTRY_POINT      = -7,
+	OVERLAY_HELPER_ERROR_EXE_LOOKUP_ENTRY_POINT      = 0x0F000007,
 	/// The overlay helper process was uanble to parse
 	/// the commandline arguments it was passed.
 	/// The helper process exepcts two arguments, and this
 	/// error occurs if it only finds one.
-	OVERLAY_HELPER_ERROR_TOO_FEW_ARGUMENTS           = -8,
+	OVERLAY_HELPER_ERROR_TOO_FEW_ARGUMENTS           = 0x0F000008,
 	/// The magic number on the command line of the overlay
 	/// helper process could not be converted to a HANDLE.
-	OVERLAY_HELPER_ERROR_EXE_INVALID_HANDLE_ARGUMENT = -9,
+	OVERLAY_HELPER_ERROR_EXE_INVALID_HANDLE_ARGUMENT = 0x0F000009,
 
 	/// The magic number passed to the overlay DLL's
 	/// OverlayHelperProcessMain function did not match
 	/// the overlay DLL's built-in magic number.
-	OVERLAY_HELPER_ERROR_DLL_MAGIC_MISMATCH          = -1000,
+	OVERLAY_HELPER_ERROR_DLL_MAGIC_MISMATCH          = 0x0FF00000,
 	/// The overlay helper process exited due to an error
 	/// in the Windows message loop.
-	OVERLAY_HELPER_ERROR_DLL_MESSAGE_LOOP            = -1001,
+	OVERLAY_HELPER_ERROR_DLL_MESSAGE_LOOP            = 0x0FF00001,
 	/// The parent death thread could not be created.
-	OVERLAY_HELPER_ERROR_DLL_PDEATH_THREAD_ERROR     = -1002,
+	OVERLAY_HELPER_ERROR_DLL_PDEATH_THREAD_ERROR     = 0x0FF00002,
 	/// The helper's WaitForSingleObject call on its parent
 	/// process failed unexpectedly.
-	OVERLAY_HELPER_ERROR_DLL_PDEATH_WAIT_FAIL        = -1003,
+	OVERLAY_HELPER_ERROR_DLL_PDEATH_WAIT_FAIL        = 0x0FF00003,
 };
 
 /// OverlayHelperErrorToString converts an OverlayHelperError value