[Libreoffice] scope of variable reduction, cppcheck-error free build and new bugs

Hello,
since I had free time, I have taken over to eliminate the "scope 
reduction" warning from cppcheck in order to reduce the noise by checks.

This has been done almost successfully, about 10 such warnings are still 
available due to #ifdefn or macros. This also allowed me to reduce other 
warnings (like hiding of var) and to find some errors introduced by 
recent changes.

Every change has been checked and done "manually", finding also some 
false positives (and one false negative). I have tested several clean 
build with different options, discovering so some too hard scope 
reduction (some #ifdefn masking some if statement). But I guess there 
are - sadly - some configurations where I did not notice that I broke 
something. (Murphy's Law lurks somewhere near us). So my apologies in 
advance.

I will push it during the week-end, once I am finished with rebasing and 
after a last clean build.

If some build option is broken, just revert the concerned commit: they 
are on purpose small and isolated. The log indicates the top directory 
and when possible the file where (the) change(s) has been done.

Regards
Pierre-André