#3 Fix build with Tcl/Tk 8.6

[Pietro Cerutti]

Hello,

this patch, against 2.0-b10, allows to build against Tcl/Tk 8.6. The greatest part of the patch is conversion from interp->result to Tcl_GetStringResult(interp) or Tcl_SetResult(interp, ...).

Also, a missing Tk_Init(tcl); caused the app to segfault on 8.6