[clangd] Use the macro name range as the definition range.

[hokein]

Summary

This also aligns with the behavior of declarations.

clangd/XRefs.cpp

std::vector<Location> findDefinitions(ParsedAST &AST, Position Pos) {
   for (auto D : Decls) {
     auto Loc = findNameLoc(D);
     auto L = makeLocation(AST, SourceRange(Loc, Loc));
     if (L)
       Result.push_back(*L);
   }
 
   for (auto Item : MacroInfos) {
-    SourceRange SR(Item.Info->getDefinitionLoc(),
-                   Item.Info->getDefinitionEndLoc());
-    auto L = makeLocation(AST, SR);
+    auto Loc = Item.Info->getDefinitionLoc();
+    auto L = makeLocation(AST, SourceRange(Loc, Loc));
     if (L)
       Result.push_back(*L);
   }
 
   return Result;
 }
 
 namespace {

unittests/clangd/XRefsTests.cpp

const char *Tests[] = {
         namespace [[ns]] {
         struct Foo { static void bar(); }
         } // namespace ns
         int main() { ^ns::Foo::bar(); }
       )cpp",
 
       R"cpp(// Macro
         #define MACRO 0
-        #define [[MACRO 1]]
+        #define [[MACRO]] 1
         int main() { return ^MACRO; }
         #define MACRO 2
         #undef macro
       )cpp",
 
       R"cpp(// Macro
        class TTT { public: int a; };
-       #define [[FF(S) if (int b = S.a) {}]]
+       #define [[FF]](S) if (int b = S.a) {}
        void f() {
          TTT t;
          F^F(t);
        }
       )cpp",
 
       R"cpp(// Forward class declaration
         class Foo;