coz: DW_FORM_sec_offset not expected for attribute (DW_AT)0x2137 / 0x2119

[timo]

coz, the causal profiler, uses libelfin to parse dwarf data, and multiple users have stumbled upon the error message in the title (plasma-umass/coz#107)

[jesperpedersen]

0x2119 and 0x2137 are GNU extensions to the DWARF format

https://github.com/gcc-mirror/gcc/blob/master/include/dwarf2.def#L441
https://github.com/gcc-mirror/gcc/blob/master/include/dwarf2.def#L454