db, buf_size, parse_call_math: track the size of returned buffers

db, buf_size, parse_call_math: track the size of returned buffers

With this change, we try to be a bit clever about how we track the size of
returned buffers.  There are lots of functions like alloc_foo() where you
pass the number of foos you want and it's allocation nr_foo * sizeof(foo)
and returns a buffer of that size.  This patch tries to calculate that.

First we record in the database when how we allocate the buffer so if we
take 24 bytes * parameter number 2 then we store that in the database.
	BUF_SIZE = "24 * <2>"

Then on the second pass if we can calculate the size we use that.

I had to fix some bugs in smatch_function_hooks.c to make this work and
those fixes got merged int this patch.

Originally the return_implies hooks and the return_states hooks were mixed
together, but now I've separated them so they are called separately.

Also there was a problem because the return_states hooks and the
implied_states hooks conflict.  They both try to set SMATCH_EXTRA.  In the
original code, we avoided this by only calling the implied_states hooks
because the implied_states are more important.  In this we call them all
but if there are implied_states they over write the return_states.

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