Fixes to support Dragonfly BSD. (#5552)

* Fix kqueue.nim and ansi_c.nim to support dragonfly.
* Fix ioselectors.nim, threads.nim to support dragonfly.
* Fix deprecated dealloc call in tioselectors.nim.
* Fix tfsmonitor.nim test to run only on Linux.
* Fix osproc.nim return wrong exit codes.
* Fix getAppFilename() for dragonfly.
* Fix proper exit code handling.

lib/system/ansi_c.nim

@@ -38,7 +38,8 @@ when defined(windows):
     SIGSEGV = cint(11)
     SIGTERM = cint(15)
 elif defined(macosx) or defined(linux) or defined(freebsd) or
-     defined(openbsd) or defined(netbsd) or defined(solaris):
+     defined(openbsd) or defined(netbsd) or defined(solaris) or
+     defined(dragonfly):
   const
     SIGABRT = cint(6)
     SIGFPE = cint(8)

lib/system/threads.nim

@@ -204,7 +204,12 @@ else:
     proc getThreadId*(): int =
       ## get the ID of the currently running thread.
       result = int(syscall(NR_gettid))
-  elif defined(macosx) or defined(bsd):
+  elif defined(dragonfly):
+    proc lwp_gettid(): int32 {.importc, header: "unistd.h".}
+
+    proc getThreadId*(): int =
+      result = int(lwp_gettid())
+  elif defined(macosx) or defined(freebsd) or defined(openbsd) or defined(netbsd):
     proc pthread_threadid_np(y: pointer; x: var uint64): cint {.importc, header: "pthread.h".}
 
     proc getThreadId*(): int =
@@ -221,7 +226,6 @@ else:
       ## get the ID of the currently running thread.
       result = int(thr_self())
 
-
 const
   emulatedThreadVars = compileOption("tlsEmulation")