Fix missing gcsafe pragma on wakeupAll proc + Fix missing stuff for Windows build

[jrainville]

Without it, I couldn't compile and got this error:

/home/jonathan/dev/nim-status-client/vendor/asynctools/asynctools/asyncsync.nim(159, 15) Error: type mismatch: got <proc (){.closure.}>
but expected one of: 
proc callSoon(cbproc: proc () {.gcsafe.})
  first type mismatch at position: 1
  required type for cbproc: proc (){.closure, gcsafe.}
  but expression 'wakeupAll' is of type: proc (){.closure.}
  This expression is not GC-safe. Annotate the proc with {.gcsafe.} to get extended error information.

expression: callSoon(wakeupAll)

edit: added another commit that fixes missing imports and casts in Windows builds