Haiku support (#596)

* Don't apply Wayland videodriver workaround on Haiku

* dirent.d_type-less type detecting in IGFD

The Dumb Way(tm). `stat`'s `st_mode` should be nicer?

* CMake check for dirent.d_type, stat-based fallback

* Move config dir setup to separate function

Nicer to work with than macro kerfuffle.

* Default sysFileDialog to off on Haiku

* Logging stuff

* Honour CMAKE_INSTALL_BINDIR

* Use find_directory on Haiku

Includes forgotten configPath line when home==NULL.

* Address PR review notes

src/check/check_dirent_type.c

@@ -0,0 +1,7 @@
+#include <dirent.h>
+
+int main(int, char**) {
+  struct dirent deTest = { };
+  unsigned char deType = deTest.d_type;
+  return 0;
+}