Fix recent compiler warnings.

Fix recent compiler warnings.

gcc-4.8.5-11.el7.x86_64

dwarf2read.c: In function ‘pc_bounds_kind dwarf2_get_pc_bounds(die_info*, CORE_ADDR*, CORE_ADDR*, dwarf2_cu*, partial_symtab*)’:
dwarf2read.c:12134:7: error: ‘range_end’ may be used uninitialized in this function [-Werror=maybe-uninitialized]
dwarf2read.c:12133:7: error: ‘range_beginning’ may be used uninitialized in this function [-Werror=maybe-uninitialized]

gdb/ChangeLog
2017-02-21  Jan Kratochvil  <jan.kratochvil@redhat.com>

	* dwarf2_rnglists_process: Initialize range_beginning and range_end.