Handle DW_AT_ranges when reading partial symtabs

Handle DW_AT_ranges when reading partial symtabs

add_partial_subprogram does not handle DW_AT_ranges, while the full
symtab reader does.  This can lead to discrepancies where a function
is not put into a partial symtab, and so is not available to "break"
and the like -- but is available if the full symtab has somehow been
read.

This patch fixes the bug by arranging to read DW_AT_ranges when
reading partial DIEs.

This is PR symtab/23331.

The new test case is derived from dw2-ranges-func.exp, which is why I
kept the copyright dates.

gdb/ChangeLog
2019-04-01  Tom Tromey  <tromey@adacore.com>

	PR symtab/23331:
	* dwarf2read.c (partial_die_info::read): Handle DW_AT_ranges.

gdb/testsuite/ChangeLog
2019-04-01  Tom Tromey  <tromey@adacore.com>

	PR symtab/23331:
	* gdb.dwarf2/dw2-ranges-main.c: New file.
	* gdb.dwarf2/dw2-ranges-psym.c: New file.
	* gdb.dwarf2/dw2-ranges-psym.exp: New file.