Fix more functions in Args to use StringRef.

This patch also marks the const char* versions as =delete to prevent
their use.  This has the potential to cause build breakages on some
platforms which I can't compile.  I have tested on Windows, Linux,
and OSX.  Best practices for fixing broken callsites are outlined in
Args.h in a comment above the deleted function declarations.

Eventually we can remove these =delete declarations, but for now they
are important to make sure that all implicit conversions from
const char * are manually audited to make sure that they do not invoke a
conversion from nullptr.

llvm-svn: 281919
diff --git a/lldb/source/Commands/CommandObjectWatchpointCommand.cpp b/lldb/source/Commands/CommandObjectWatchpointCommand.cpp
index b576ce8..c67bae0 100644
--- a/lldb/source/Commands/CommandObjectWatchpointCommand.cpp
+++ b/lldb/source/Commands/CommandObjectWatchpointCommand.cpp
@@ -318,7 +318,8 @@
 
       case 'e': {
         bool success = false;
-        m_stop_on_error = Args::StringToBoolean(option_arg, false, &success);
+        m_stop_on_error = Args::StringToBoolean(
+            llvm::StringRef::withNullAsEmpty(option_arg), false, &success);
         if (!success)
           error.SetErrorStringWithFormat(
               "invalid value for stop-on-error: \"%s\"", option_arg);