[Haiku] Create resource file.

Vector icon created by Giovanni, RDEF by Arfonzo, some tweaks by me.
[Haiku] Build system tweaks for Haiku.

Patch by Arfonzo.
[Haiku] Doesn't support readdir's d_type flag...

...which is a Linux thing and not part of the POSIX standard. Haiku may support it eventually, but as of today it does not.
[Haiku] Enable backtrace generation.
[Haiku] Link to -lexecinfo.
Set -lexecinfo in main.pro...

...because it's used in main.cpp and setting it in libs.pro is not enough.
Merge pull request #1408 from waddlesplash/haiku-fixes

Fixes so that QupZilla can run on Haiku