Fix #3256 (Null pointer dereference not detected)

http://sourceforge.net/apps/trac/cppcheck/ticket/3256
It is now detected if --inconclusive command line argument is given (the argument is unofficial currently)

lib/checknullpointer.cpp

@@ -817,9 +817,14 @@ void CheckNullPointer::nullPointerByCheckAndDeRef()
                 if (Token::simpleMatch(tok2, ") ;") &&
                     (Token::Match(tok2->link()->tokAt(-2), "[;{}.] %var% (") ||
                      Token::Match(tok2->link()->tokAt(-5), "[;{}] ( * %var% ) ("))) {
-                    // noreturn function?
-                    if (tok2->strAt(2) == "}")
-                        break;
+                    if (!_settings->inconclusive) {
+                        // noreturn function?
+                        // If inside null pointer check we unknown function call, we must
+                        // assume that it can terminate the program and possible null pointer
+                        // error wont ever happen.
+                        if (tok2->strAt(2) == "}")
+                            break;
+                    }
 
                     // init function (global variables)
                     const SymbolDatabase *symbolDatabase = _tokenizer->getSymbolDatabase();

test/testnullpointer.cpp

@@ -1176,6 +1176,14 @@ private:
               "}\n");
         ASSERT_EQUALS("", errout.str());
 
+        check("void foo(char *p) {\n"
+              "    if (!p) {\n"
+              "        abort();\n"
+              "    }\n"
+              "    *p = 0;\n"
+              "}\n", true);
+        ASSERT_EQUALS("[test.cpp:5]: (error) Possible null pointer dereference: p - otherwise it is redundant to check if p is null at line 2\n", errout.str());
+
         check("void foo(char *p) {\n"
               "    if (!p) {\n"
               "        (*bail)();\n"