Fix LSR gen: \\ in texidoc needs to be escaped once more (used in regexp!)

Fix LSR gen: \\ in texidoc needs to be escaped once more (used in regexp!)

In makelsr.py, we read in the .texidoc file and insert its contents into the
snippet page. Unfortunately, this is done using a regexp, so \\ is understood
as ONE escaped backslash. Thus, I simply replace \\ by \\\\ before inserting...