* Fix some false positive in loop forward analysis
In cases like:
```
bool b();
void f()
{
int val[50];
int i, sum=0;
for (i = 1; b() && i < 50; i++)
sum += val[i];
for (; i < 50; i++)
sum -= val[i];
}
```
The forward analysis assumed the second loop was entered, and we ended
up with false positive in it:
`Array 'val[50]' accessed at index 50, which is out of bounds`
* Fix style
Format-string arguments are now marked to have `in` direction, except
for `scan`-functions (like `scanf`) where these arguments are explicitly
marked to have `out` direction.
* Set correct type and size of string and char literals
Use that string and char literal tokens store the prefix. This makes
it possible to distinghuish between different type of string literals
(i.e., utf8 encoded strings, utf16, wide strings, etc) which have
different type.
When the tokens holding the string and character values have the correct
type, it is possible to improve Token::getStrSize() to give the correct
result for all string types. Previously, it would return the number of
characters in the string, i.e., it would give the wrong size unless
the type of the string was char*.
Since strings now can have different size (in number of bytes) and
length (in number of elements), add a new helper function that returns
the number of characters. Checkers have been updated to use the correct
functions.
Having the size makes it possible to find more problems with prefixed
strings, and to reduce false positives, for example in the buffer
overflow checker.
Also, improve the stringLiteralWrite error message to also print the
prefix of the string (if there is one).
* Add comment and update string length
Building with enhanced clang warnings indicated a large number of
instances with the warning:
`warning: zero as null pointer constant`
Recommended practice in C++11 is to use `nullptr` as value for
a NULL or empty pointer value. All instances where this warning
was encountered were corrected in this commit.
Where warning was encountered in dependency code (i.e. external library)
no chnages were made. Patching will be offered upstream.
