Add std::move warnings to -Wmost, which also brings them under -Wall

[rtrieu]

Summary

This change moves the std::move warnings into -Wmove and puts -Wmove into -Wmost, which is included by -Wall. See previous discussion at:

http://lists.cs.uiuc.edu/pipermail/cfe-commits/Week-of-Mon-20150427/128128.html
http://lists.cs.uiuc.edu/pipermail/cfe-commits/Week-of-Mon-20150427/128392.html
http://lists.cs.uiuc.edu/pipermail/cfe-commits/Week-of-Mon-20150504/128435.html

[thakis]

lgtm

[thakis]

Can you land this?

include/clang/Basic/DiagnosticGroups.td

def Format2 : DiagGroup<"format=2",
                         [FormatNonLiteral, FormatSecurity, FormatY2K]>;
 
 def TypeSafety : DiagGroup<"type-safety">;
 
 def IntToVoidPointerCast : DiagGroup<"int-to-void-pointer-cast">;
 def IntToPointerCast : DiagGroup<"int-to-pointer-cast",
                                  [IntToVoidPointerCast]>;
 
+def Move : DiagGroup<"move", [PessimizingMove, RedundantMove, SelfMove]>;
+
 def Extra : DiagGroup<"extra", [
     MissingFieldInitializers,
     IgnoredQualifiers,
     InitializerOverrides,
     SemiBeforeMethodBody,
     MissingMethodReturnType,
     SignCompare,
     UnusedParameter
   ]>;
 
 def Most : DiagGroup<"most", [
     CharSubscript,
     Comment,
     DeleteNonVirtualDtor,
     Format,
     Implicit,
     MismatchedTags,
     MissingBraces,
+    Move,
     MultiChar,
     Reorder,
     ReturnType,
     SelfAssignment,
     SelfMove,
     SizeofArrayArgument,
     SizeofArrayDecay,
     StringPlusInt,