Support DWARF v3

[danielocfb]

I just played around attempting to test DWARF v2 support. It turns out at least on gcc, that basically implies usage of extensions from later standards. So what ends up happening is that when a binary is created with v2 DWARF, it contains v3 bits and we don't support that.

There exists the -gstrict-dwarf flag, but it seemingly does nothing (?). The bottom line is that supporting DWARF v2 but explicitly not v3 could still mean that we have big gaps in what we actually support.

I didn't see the above issue with clang (it did not appear to be emitting v3 bits when asked for v2), though there we see other issues...