fixed -Wdeprecated-this-capture Clang C++20 warnings

example:
```
/home/user/CLionProjects/cppcheck/lib/pathmatch.cpp:37:37: warning: implicit capture of 'this' with a capture default of '=' is deprecated [-Wdeprecated-this-capture]
   37 |         return match(pattern, path, mBasepath, mode, mSyntax);
      |                                     ^
/home/user/CLionProjects/cppcheck/lib/pathmatch.cpp:36:63: note: add an explicit capture of 'this' to capture '*this' by reference
   36 |     return std::any_of(mPatterns.cbegin(), mPatterns.cend(), [=] (const std::string &pattern) {
      |                                                               ^
      |                                                                , this
```

Author: firewave

gui/resultstree.cpp

@@ -22,6 +22,7 @@
 #include "applicationlist.h"
 #include "checkers.h"
 #include "common.h"
+#include "config.h"
 #include "erroritem.h"
 #include "errorlogger.h"
 #include "errortypes.h"
@@ -702,15 +703,15 @@ void ResultsTree::contextMenuEvent(QContextMenuEvent * e)
                 {
                     auto *action = new QAction(tr("No tag"), tagMenu);
                     tagMenu->addAction(action);
-                    connect(action, &QAction::triggered, [=]() {
+                    connect(action, &QAction::triggered, [EXPLICIT_THIS]() {
                         tagSelectedItems(QString());
                     });
                 }
 
                 for (const QString& tagstr : currentProject->getTags()) {
                     auto *action = new QAction(tagstr, tagMenu);
                     tagMenu->addAction(action);
-                    connect(action, &QAction::triggered, [=]() {
+                    connect(action, &QAction::triggered, [EXPLICIT_THIS]() {
                         tagSelectedItems(tagstr);
                     });
                 }

lib/config.h

@@ -131,6 +131,12 @@
 #  define RET_NONNULL
 #endif
 
+#if __cplusplus >= 202002L
+#  define EXPLICIT_THIS =, this
+#else
+#  define EXPLICIT_THIS =
+#endif
+
 #define REQUIRES(msg, ...) class=typename std::enable_if<__VA_ARGS__::value>::type
 
 // Use the nonneg macro when you want to assert that a variable/argument is not negative

lib/pathmatch.cpp

@@ -33,7 +33,7 @@ PathMatch::PathMatch(std::vector<std::string> patterns, std::string basepath, Sy
 
 bool PathMatch::match(const std::string &path, Filemode mode) const
 {
-    return std::any_of(mPatterns.cbegin(), mPatterns.cend(), [=] (const std::string &pattern) {
+    return std::any_of(mPatterns.cbegin(), mPatterns.cend(), [&] (const std::string &pattern) {
         return match(pattern, path, mBasepath, mode, mSyntax);
     });
 }