Delete some more dead includes.

This breaks the cycle between Target and PluginLanguageC++, reducing
the overall cycle count from 43 to 42.

llvm-svn: 298561
diff --git a/lldb/source/Interpreter/OptionValueString.cpp b/lldb/source/Interpreter/OptionValueString.cpp
index 89367a9..149ccbc 100644
--- a/lldb/source/Interpreter/OptionValueString.cpp
+++ b/lldb/source/Interpreter/OptionValueString.cpp
@@ -14,6 +14,7 @@
 // C++ Includes
 // Other libraries and framework includes
 // Project includes
+#include "lldb/Host/OptionParser.h"
 #include "lldb/Interpreter/Args.h"
 #include "lldb/Utility/Stream.h"