Clang: Provide tooltips

This includes also the query data for the help system (F1) for an
identifier under cursor.

Regressions (libclang changes necessary):
 - Function signatures do not contain default values.
 - Aliases are not resolved for/at:
   - template types
   - qualified name of a type

Fixes/Improvements:
 - Resolve "auto"
 - On a template type, show also the template parameter.
 - For a typedef like
     typedef long long superlong;
   the tooltip was "long long superlong", which was confusing.
   Now, "long long" is shown.

New:
 - Show first or \brief paragraph of a documentation comment.
 - Show size of a class at definition.
 - Show size of a field member in class definition.

Task-number: QTCREATORBUG-11259
Change-Id: Ie1a07930d0e882015d07dc43e35bb81a685cdeb8
Reviewed-by: Marco Bubke <marco.bubke@qt.io>

tests/unit/unittest/data/tooltipinfo.cpp

@@ -0,0 +1,180 @@
+void f(int foo, const int *cfoo)
+{
+    foo++;
+    cfoo++;
+}
+
+
+
+struct Foo { int member = 0; };
+int g(const Foo &foo)
+{
+    return foo.member;
+    const Foo bar;
+    bar;
+}
+
+struct Bar { virtual ~Bar(); int mem(){} virtual int virtualConstMem() const; };
+void h(const Foo &foo, Bar &bar)
+{
+    g(foo);
+    bar.mem();
+    bar.virtualConstMem();
+}
+
+
+template <typename T>
+void t(int foo) { (void)foo; }
+void c()
+{
+    t<Foo>(3);
+}
+
+
+
+/**
+ * \brief This is a crazy function.
+ */
+void documentedFunction();
+void d()
+{
+    documentedFunction();
+}
+
+
+
+enum EnumType { V1, V2, Custom = V2 + 5 };
+EnumType e()
+{
+    return EnumType::Custom;
+}
+
+
+
+template <typename T> struct Baz { T member; };
+void t2(const Baz<int> &b) {
+    Baz<int> baz; baz = b;
+}
+
+#include "tooltipinfo.h"
+
+
+
+#define MACRO_FROM_MAINFILE(x) x + 3
+void foo()
+{
+    MACRO_FROM_MAINFILE(7);
+    MACRO_FROM_HEADER(7);
+}
+
+
+
+namespace N { struct Muu{}; }
+namespace G = N;
+void o()
+{
+    using namespace N;
+    Muu muu; (void)muu;
+}
+void n()
+{
+    using namespace G;
+    Muu muu; (void)muu;
+}
+void q()
+{
+    using N::Muu;
+    Muu muu; (void)muu;
+}
+
+
+
+struct Sizes
+{
+    char memberChar1;
+    char memberChar2;
+};
+enum class FancyEnumType { V1, V2 };
+union Union
+{
+    char memberChar1;
+    char memberChar2;
+};
+
+
+
+namespace X {
+namespace Y {
+}
+}
+
+
+
+template<typename T> struct Ptr {};
+struct Nuu {};
+
+typedef Ptr<Nuu> PtrFromTypeDef;
+using PtrFromTypeAlias = Ptr<Nuu>;
+template<typename T> using PtrFromTemplateTypeAlias = Ptr<T>;
+
+void y()
+{
+    PtrFromTypeDef b; (void)b;
+    PtrFromTypeAlias a; (void)a;
+    PtrFromTemplateTypeAlias<Nuu> c; (void)c;
+}
+
+
+
+template <typename T> struct Zii {};
+namespace U { template <typename T> struct Yii {}; }
+void mc()
+{
+    using namespace U;
+    Zii<int> zii; (void) zii;
+    Yii<int> yii; (void) yii;
+}
+
+
+
+namespace A { struct X {}; }
+namespace B = A;
+void ab()
+{
+    B::X x; (void)x;
+}
+
+
+
+namespace N {
+struct Outer
+{
+    template <typename T> struct Inner {};
+    Inner<int> inner;
+};
+}
+
+
+
+void f();
+namespace R { void f(); }
+void f(int param);
+void z(int = 1);
+void user()
+{
+    f();
+    R::f();
+    f(1);
+    z();
+}
+
+
+
+
+void autoTypes()
+{
+    auto a = 3; (void)a;
+    auto b = EnumType::V1; (void)b;
+    auto c = Bar(); (void)c;
+    auto d = Zii<int>(); (void)d;
+}