inlined ~AssertionHandler(), and changed getConfig to return
shared_ptr const reference instead of by value (very expensive for
shared_ptr's).
Further work on #1086.
Brings test from 0m20.635s to 0m17.186s
Swept:
`-Wpadded` in some places (where it caused extra size, instead of just
saying "hey, we padded struct at the end to align, just as standard says")
`-Wweak-vtables` everywhere (Clang)
`-Wexit-time-destructors` everywhere (Clang)
`-Wmissing-noreturn` everywhere (Clang)
The last three are enabled for Clang compilation going forward.
Also enabled `-Wunreachable-code` for Clang and GCC
