extra, function_hooks: fix handling of casted function calls

extra, function_hooks: fix handling of casted function calls

If we have code like this:
	unsigned int frob();
	...
	int x = (unsigned char)frob();

There were several problems with this.  When we're changing the string
from the database "0-u32max" to a range_list then we need to do that with
a unsigned int type.  The current code was using unsigned char.  After we
have the unsigned int then we can cast it to unsigned char.

Also in smatch_extra.c it was looking at the cast operation and not
seeing that it was a function call.  It meant that we set the value then
set it again properly later.  It's doesn't cause a bug, but it's not
pretty.

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>