C++: Address review comments.

Author: MathiasVP

cpp/ql/test/library-tests/dataflow/taint-tests/localTaint.expected

@@ -6033,10 +6033,12 @@
 | taint.cpp:617:7:617:11 | ref arg dest3 | taint.cpp:618:8:618:12 | dest3 |  |
 | taint.cpp:618:8:618:12 | dest3 | taint.cpp:618:7:618:12 | * ... | TAINT |
 | taint.cpp:625:33:625:38 | source | taint.cpp:628:17:628:22 | source |  |
-| taint.cpp:628:7:628:15 | call to _strnextc | taint.cpp:628:3:628:23 | ... = ... |  |
+| taint.cpp:628:7:628:15 | call to _strnextc | taint.cpp:628:3:628:25 | ... = ... |  |
 | taint.cpp:628:7:628:15 | call to _strnextc | taint.cpp:629:8:629:8 | c |  |
 | taint.cpp:628:7:628:15 | call to _strnextc | taint.cpp:630:10:630:10 | c |  |
-| taint.cpp:628:17:628:22 | source | taint.cpp:628:7:628:15 | call to _strnextc | TAINT |
+| taint.cpp:628:17:628:22 | source | taint.cpp:628:17:628:24 | ... ++ |  |
+| taint.cpp:628:17:628:24 | ... ++ | taint.cpp:628:7:628:15 | call to _strnextc | TAINT |
+| taint.cpp:628:17:628:24 | ... ++ | taint.cpp:628:17:628:22 | source | TAINT |
 | taint.cpp:631:6:631:14 | call to _strnextc | taint.cpp:631:2:631:18 | ... = ... |  |
 | taint.cpp:631:6:631:14 | call to _strnextc | taint.cpp:632:7:632:7 | c |  |
 | taint.cpp:631:16:631:17 |  | taint.cpp:631:6:631:14 | call to _strnextc | TAINT |

cpp/ql/test/library-tests/dataflow/taint-tests/taint.cpp

@@ -625,7 +625,7 @@ unsigned int _strnextc(const char*);
 void test__strnextc(const char* source) {
 	unsigned c = 0;
 	do {
-		c = _strnextc(source);
+		c = _strnextc(source++);
 		sink(c); // $ ast,ir
 	} while(c != '\0');
 	c = _strnextc("");