gdb.dwarf2: Don't hardcode certain constants in Dwarf::assemble constructs

gdb.dwarf2: Don't hardcode certain constants in Dwarf::assemble constructs

Two tests in gdb.dwarf2, data-loc.exp and dynarr-ptr.exp assume that
sizeof(int) is 4.  This patch looks up the integer size and uses this
constant for DW_AT_byte_size, DW_AT_lower_bound, and DW_AT_upper_bound.

I discovered this problem while looking at test results for this
msp430 multilib:

msp430-sim/-msim/-mcpu=msp430x/-mlarge/-mdata-region=either/-mcode-region=either

It fixes the following set of failures:

FAIL: gdb.dwarf2/dynarr-ptr.exp: print foo.three_ptr.all'first
FAIL: gdb.dwarf2/dynarr-ptr.exp: print foo.three_ptr'first
FAIL: gdb.dwarf2/dynarr-ptr.exp: print foo.three_ptr_tdef.all'first
FAIL: gdb.dwarf2/dynarr-ptr.exp: print foo.three_ptr_tdef'first
FAIL: gdb.dwarf2/dynarr-ptr.exp: print foo.five_ptr.all'first
FAIL: gdb.dwarf2/dynarr-ptr.exp: print foo.five_ptr'first
FAIL: gdb.dwarf2/dynarr-ptr.exp: print foo.five_ptr_tdef.all'first
FAIL: gdb.dwarf2/dynarr-ptr.exp: print foo.five_ptr_tdef'first
FAIL: gdb.dwarf2/data-loc.exp: print foo.three
FAIL: gdb.dwarf2/data-loc.exp: print foo.three(1)
FAIL: gdb.dwarf2/data-loc.exp: print foo.three(2)
FAIL: gdb.dwarf2/data-loc.exp: print foo.three(3)
FAIL: gdb.dwarf2/data-loc.exp: print foo.three_tdef
FAIL: gdb.dwarf2/data-loc.exp: print foo.three_tdef(1)
FAIL: gdb.dwarf2/data-loc.exp: print foo.three_tdef(2)
FAIL: gdb.dwarf2/data-loc.exp: print foo.three_tdef(3)
FAIL: gdb.dwarf2/data-loc.exp: print foo.five
FAIL: gdb.dwarf2/data-loc.exp: print foo.five(2)
FAIL: gdb.dwarf2/data-loc.exp: print foo.five(3)
FAIL: gdb.dwarf2/data-loc.exp: print foo.five(4)
FAIL: gdb.dwarf2/data-loc.exp: print foo.five(5)
FAIL: gdb.dwarf2/data-loc.exp: print foo.five(6)
FAIL: gdb.dwarf2/data-loc.exp: print foo.five_tdef
FAIL: gdb.dwarf2/data-loc.exp: print foo.five_tdef(2)
FAIL: gdb.dwarf2/data-loc.exp: print foo.five_tdef(3)
FAIL: gdb.dwarf2/data-loc.exp: print foo.five_tdef(4)
FAIL: gdb.dwarf2/data-loc.exp: print foo.five_tdef(5)
FAIL: gdb.dwarf2/data-loc.exp: print foo.five_tdef(6)
FAIL: gdb.dwarf2/data-loc.exp: print foo__three
FAIL: gdb.dwarf2/data-loc.exp: print foo__three_tdef
FAIL: gdb.dwarf2/data-loc.exp: print foo__five
FAIL: gdb.dwarf2/data-loc.exp: print foo__five_tdef

As I recall, there are still (other) problems with msp430 multilibs
which don't use -mlarge.

gdb/testsuite/ChangeLog:

	* gdb.dwarf2/data-loc.exp (Dwarf::assemble): Don't hardcode
	value associated with DW_AT_byte_size.
	* gdb.dwarf2/dynarr-ptr.exp (Dwarf::assemble): Don't hardcode
	constants for DW_AT_byte_size, DW_AT_lower_bound, and
	DW_AT_upper_bound.