Use spaces, not tabs, for indentation.

There were a bunch of 4-space tab characters in the file, which is 1)
not the way UN*Xes work and 2) not what the modelines say; replace them
with 4 spaces, and further adjust some indentation.

Change the modelines to turn tab-to-space expansion on.

Change-Id: I7e22294e928ef95ab9f5d61f5d0e8abfe18cfb4e
Reviewed-on: https://code.wireshark.org/review/36738
Reviewed-by: Guy Harris <gharris@sonic.net>

epan/dissectors/packet-fpp.c

@@ -689,9 +689,9 @@ proto_reg_handoff_fpp(void)
  * Local variables:
  * c-basic-offset: 4
  * tab-width: 8
- * indent-tabs-mode: t
+ * indent-tabs-mode: nil
  * End:
  *
- * vi: set shiftwidth=4 tabstop=8 noexpandtab:
+ * vi: set shiftwidth=4 tabstop=8 expandtab:
  * :indentSize=4:tabSize=8:noTabs=false:
  */