Add location support to BIR::Statement

Add location support to BIR::Statement

This commit adds location_t to BIR::Statement where type is ASSIGNMENT
this information will be later used for reporting borrow-checking
errors.

gcc/rust/ChangeLog:

	* checks/errors/borrowck/rust-bir-builder-expr-stmt.cc
	(ExprStmtBuilder::visit): Added location parameter.
	* checks/errors/borrowck/rust-bir-builder-internal.h: Likewise.
	* checks/errors/borrowck/rust-bir-builder-lazyboolexpr.h:
	Likewise.
	* checks/errors/borrowck/rust-bir-builder-pattern.h: Likewise.
	* checks/errors/borrowck/rust-bir-builder.h: Likewise.
	* checks/errors/borrowck/rust-bir.h: Likewise.

Signed-off-by: Kushal Pal <kushalpal109@gmail.com>