posix.cfg: Fixed FP bufferOverlap-warning of bcopy() and added more tests.

cfg/posix.cfg

@@ -3935,11 +3935,11 @@ The function 'mktemp' is considered to be dangerous due to race conditions and s
     </arg>
     <warn severity="style" reason="Obsolescent" alternatives="scalbln,scalblnf,scalbln,scalbn,scalbnf,scalbnl"/>
   </function>
+  <!-- https://man7.org/linux/man-pages/man3/bcopy.3.html -->
   <!-- void bcopy(const void *s1, void *s2, size_t n); -->
   <function name="bcopy">
     <noreturn>false</noreturn>
     <leak-ignore/>
-    <not-overlapping-data ptr1-arg="1" ptr2-arg="2" size-arg="3"/>
     <arg nr="1" direction="in">
       <not-null/>
       <not-uninit/>

test/cfg/posix.c

@@ -300,8 +300,20 @@ void overlappingWriteFunction_bcopy(char *buf, const size_t count)
     // cppcheck-suppress bcopyCalled
     bcopy(&buf[0], &buf[3], 3U);    // no-overlap
     // cppcheck-suppress bcopyCalled
-    // cppcheck-suppress overlappingWriteFunction
-    bcopy(&buf[0], &buf[3], 4U);
+    bcopy(&buf[0], &buf[3], 4U);    // The result is correct, even when both areas overlap.
+}
+
+void nullPointer_bcopy(const void *src, void *dest, size_t n)
+{
+    // No warning shall be shown:
+    // cppcheck-suppress bcopyCalled
+    bcopy(src, dest, n);
+    // cppcheck-suppress bcopyCalled
+    // cppcheck-suppress nullPointer
+    bcopy(NULL, dest, n);
+    // cppcheck-suppress bcopyCalled
+    // cppcheck-suppress nullPointer
+    bcopy(src, NULL, n);
 }
 
 void overlappingWriteFunction_memccpy(unsigned char *src, unsigned char *dest, int c, size_t count)