[io_mesh_qfmdl] Use an int for NLA start frame

At at some stage blender enforced frames being integers (In the past,
there was support for fractional, I think, but I also seem to remember
it not working) (yes, for anybody looking, this commit message is more
or less copied from io_object_mu).

tools/io_mesh_qfmdl/import_mdl.py

@@ -226,7 +226,7 @@ def build_actions(mdl):
     ad = sk.animation_data_create()
     track = ad.nla_tracks.new();
     track.name = mdl.name
-    start_frame = 1.0
+    start_frame = 1
     for frame in mdl.frames:
         act = bpy.data.actions.new(frame.name)
         data = []
@@ -260,7 +260,7 @@ def build_actions(mdl):
                 data.append((k, co))
         set_keys(act, data)
         track.strips.new(act.name, start_frame, act)
-        start_frame += act.frame_range[1]
+        start_frame += int(act.frame_range[1])
 
 def merge_frames(mdl):
     def get_base(name):