flow: parse global variables before parsing functions

flow: parse global variables before parsing functions

When we're parsing a file, then I want to parse all the variable
definitions first, then the functions.  I save all the SMATCH_EXTRA states
in a stree called global_states.  Right now I don't use it, but later I
will figure out which of those variables are const and look them up in
the global_states stree.

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