include tree.h instead of tree-core.h in expr.h

[Prathamesh Kulkarni <bilbotheelffriend at gmail dot com>]

In expr.h:

/* For tree_fits_[su]hwi_p, tree_to_[su]hwi, fold_convert, size_binop,
   ssize_int, TREE_CODE, TYPE_SIZE, int_size_in_bytes,    */
#include "tree-core.h"

However the functions tree_to_shwi(), tree_fits_shwi(), etc.
are not declared in tree-core.h, but in tree.h

This is not a problem because tree_to_shwi() gets called from within
macros in expr.h,
(eg: from ADD_PARM_SIZE and SUB_PARM_SIZE macros), and when these
macros are called, tree.h has been already included in that
translation unit before including expr.h (for example, in alias.c
tree.h, is included before expr.h).

I am replacing macros by static inline functions
(http://gcc.gnu.org/ml/gcc/2013-12/msg00148.html), changing
ADD_PARM_SIZE() from macro to
function now gives an error, that tree_to_shwi() (and other things
like ssizetype, etc.) are not defined in scope. Including tree.h
removes these errors.

Would it be better to include tree.h instead of tree-core.h (tree.h
includes tree-core.h anyway), or shall I leave these macros untouched
?

Thanks and Regards,
Prathamesh