switch from gimple to gimple*

This renames the gimple_statement_base struct to gimple removes the
typedef of gimple_statement_base * to gimple, and then adjusts all of
the places that use the type.

gcc/ChangeLog:

2015-09-19  Trevor Saunders  <tbsaunde@tbsaunde.org>

	* coretypes.h (gimple): Change typedef to be a forward
	declaration.
	* gimple.h (gimple_statement_base): rename to gimple.
	* (all functions and types using gimple): Adjust.
	* *.[ch]: Likewise.

gcc/cp/ChangeLog:

2015-09-19  Trevor Saunders  <tbsaunde@tbsaunde.org>

	* cp-gimplify.c (gimplify_must_not_throw_expr): Adjust.

From-SVN: r227941