C: Parser: Support parsing of c99 designated initializers

In case:

    int a[6] = { [4] = 29, [2] = 15 };
    struct point { int x, y; };
    struct point p = { .y = 3, .x = 2 };

Grammar change when c99 language feature is enabled:
old grammar:

    braced-init-list :: '{' initializer-list '}'

new grammar:

    braced-init-list :: '{' designated-initializer-list '}'
    designated-initializer-list :: designated-initializer (',' designated-initializer )*
    designated-initializer :: designator* initializer-clause
    designator :: '.' identifier
                | '[' constant-expression ']'

Task-number: QTCREATORBUG-1902
Change-Id: Ib99d6f553f8d0f50ba3eff86f3a2e86d73372426
Reviewed-by: Nikolai Kosjar <nikolai.kosjar@digia.com>

src/libs/3rdparty/cplusplus/AST.h

@@ -161,6 +161,8 @@ public:
     virtual DeclaratorIdAST *asDeclaratorId() { return 0; }
     virtual DecltypeSpecifierAST *asDecltypeSpecifier() { return 0; }
     virtual DeleteExpressionAST *asDeleteExpression() { return 0; }
+    virtual DesignatedInitializerAST *asDesignatedInitializer() { return 0; }
+    virtual DesignatorAST *asDesignator() { return 0; }
     virtual DestructorNameAST *asDestructorName() { return 0; }
     virtual DoStatementAST *asDoStatement() { return 0; }
     virtual DynamicExceptionSpecificationAST *asDynamicExceptionSpecification() { return 0; }
@@ -4527,6 +4529,72 @@ protected:
     virtual bool match0(AST *, ASTMatcher *);
 };
 
+class DesignatorAST: public AST
+{
+public:
+    enum Type
+    {
+        Invalid,
+        Dot,
+        Bracket
+    };
+    Type type;
+    union Designator
+    {
+        struct DotDesignator
+        {
+            unsigned dot_token;
+            unsigned identifier_token;
+        } dot;
+        struct BracketDesignator
+        {
+            unsigned lbracket_token;
+            ExpressionAST *expression;
+            unsigned rbracket_token;
+        } bracket;
+    } u;
+
+public:
+    DesignatorAST()
+        : type(Invalid)
+    {}
+
+    virtual DesignatorAST *asDesignator() { return this; }
+    virtual unsigned firstToken() const;
+    virtual unsigned lastToken() const;
+
+    virtual DesignatorAST *clone(MemoryPool *pool) const;
+
+protected:
+    virtual void accept0(ASTVisitor *visitor);
+    virtual bool match0(AST *, ASTMatcher *);
+};
+
+class DesignatedInitializerAST: public ExpressionAST
+{
+public:
+    DesignatorListAST *designator_list;
+    unsigned equal_token;
+    ExpressionAST *initializer;
+
+public:
+    DesignatedInitializerAST()
+        : designator_list(0)
+        , equal_token(0)
+        , initializer(0)
+    {}
+
+    virtual DesignatedInitializerAST *asDesignatedInitializer() { return this; }
+    virtual unsigned firstToken() const;
+    virtual unsigned lastToken() const;
+
+    virtual DesignatedInitializerAST *clone(MemoryPool *pool) const;
+
+protected:
+    virtual void accept0(ASTVisitor *visitor);
+    virtual bool match0(AST *, ASTMatcher *);
+};
+
 } // namespace CPlusPlus
 
 #endif // CPLUSPLUS_AST_H