Problems with slurs when key signature changes at linebreaks

[Francesco Guglie]

Hello to everybody!
I'm using lilypond 2.10.20 on a GNU/Linux system and I'm having some troubles 
with slurs and phrasing slurs when key and time signatures change at a 
linebreak and slurs must go across such a linebreak.
Here a small piece of code that shows the situation I'm writing about:

%%% LILYCODE BEGINS %%%

\version "2.10.20"
\score {
  \new Staff \relative c'' {
      g1(^"normal slur"  | a | b | g
        \key g \major
        \time 2/2
        \break
    | c) | a\(^"phrasing slur" | b | g
       \key c \major
       \time 4/4
       \break
   | c\) | b | a | g 
    }  
}

%%% LILYCODE ENDS %%%

I would like both slurs and phrasing slurs to stop at barline *before* the 
cautionary key signature change (not only before the time signature, as in 
normal slur case) and I would like to have normal slurs at the beginning of 
the new line starting as the phrasing slurs: after the time signature. 
I've been looking through configuration files in /ly and /scm in the 
installation subdirectories but I cannot understand what I should change to 
make slurs start and stop as I need.
If anyone has any suggestions, I would be very grateful to know them.
Thank you!

Francesco Guglie