This patch makes `dwarfdump` show the `DW_AT_APPLE_property_name` of a
referenced `DW_TAG_APPLE_property` (similar to how we show the name of a
referenced `DW_AT_type`). Eventually we'll extend this to the DWARFv6
property tags too.
Before:
```
0x00000013: DW_TAG_APPLE_property
DW_AT_APPLE_property_name ("propertyName")
0x0000001b: DW_TAG_member
DW_AT_name ("_ivar")
DW_AT_APPLE_property (0x00000013)
```
After:
```
0x00000013: DW_TAG_APPLE_property
DW_AT_APPLE_property_name ("propertyName")
0x0000001b: DW_TAG_member
DW_AT_name ("_ivar")
DW_AT_APPLE_property (0x00000013 "propertyName")
```