1. bug fixed: Unicode characters that are not mapped to TeX macros used to

1. bug fixed: Unicode characters that are not mapped to TeX macros used to
   be post-fixed with a blank
2. bug fixed: the textual pretty-printer does not implement the same
   spacing politics of GtkMathView. Since that politics is very very complex
   to implement, I try a different solution: we explicitly insert a space
   where we want one. The widget does not seem to be disturbed by this.
   This way the let ... rec and match ... with constructs are now printed
   correctly and they can be read back.
3. syntax change: applicative patterns no longer require parentheses around
   them