handle DW_AT_type on an enumeration

handle DW_AT_type on an enumeration

DWARF allows an enumeration type to have a DW_AT_type.  GDB doesn't
recognize this, but there is a patch to change GCC to emit it, and a
DWARF proposal to further allow an enum type with a DW_AT_type to omit
the DW_AT_byte_size.  This patch changes gdb to implement this.

Built and regtested on x86-64 Fedora 20.

2014-04-14  Tom Tromey  <tromey@redhat.com>

	* dwarf2read.c (read_enumeration_type): Handle DW_AT_type.

2014-04-14  Tom Tromey  <tromey@redhat.com>

	* gdb.dwarf2/enum-type.exp: New file.