RULE-8-7: Support use in headers.

Author: lcartey

c/misra/src/rules/RULE-8-7/ShouldNotBeDefinedWithExternalLinkage.ql

@@ -40,7 +40,8 @@ predicate isReferencedInTranslationUnit(
   ExternalIdentifiers e, ExternalIdentifierReference r, TranslationUnit t
 ) {
   r.getExternalIdentifierTarget() = e and
-  r.getFile() = t
+  // Used within the translation unit or an included header
+  r.getFile() = t.getAUserFile()
 }
 
 from ExternalIdentifiers e, ExternalIdentifierReference a1, TranslationUnit t1

c/misra/test/rules/RULE-8-7/ShouldNotBeDefinedWithExternalLinkage.expected

@@ -1,3 +1,4 @@
+| test2.h:2:13:2:14 | f6 | Declaration with external linkage is accessed in only one translation unit $@. | test2.h:3:22:3:23 | call to f6 | call to f6 |
 | test.c:3:5:3:6 | i1 | Declaration with external linkage is accessed in only one translation unit $@. | test.c:11:3:11:4 | i1 | i1 |
 | test.c:4:5:4:6 | i2 | Declaration with external linkage is accessed in only one translation unit $@. | test.c:12:3:12:4 | i2 | i2 |
 | test.c:6:6:6:7 | f2 | Declaration with external linkage is accessed in only one translation unit $@. | test.c:14:3:14:4 | call to f2 | call to f2 |

c/misra/test/rules/RULE-8-7/test1.c

@@ -1,4 +1,4 @@
-#include "test.h"
+#include "test2.h"
 void f() {
   i = 0;
   f1();

c/misra/test/rules/RULE-8-7/test2.h

@@ -0,0 +1,3 @@
+#include "test.h"
+extern void f6() {} // NON_COMPLIANT
+static void test() { f6(); }