GCC 9

[Stephan Bergmann]

FYI, I did a Linux x86_64 master build against recent GCC trunk (towards 
GCC 9) the other day.  That mainly caused new -Wrestrict and 
-Wdeprecated-copy warnings, all of which have been addressed in the LO 
master sources.  Except for one bogus -Wrestrict that is tracked at 
<https://gcc.gnu.org/bugzilla/show_bug.cgi?id=86196> "[9 Regression] 
Bogus -Wrestrict on memcpy between array elements at unequal indices". 
If that GCC bug doesn't get fixed in time, I have 
<https://gerrit.libreoffice.org/#/c/58173/> "Work around GCC trunk 
(towards GCC 9) bug for now" that we could apply to LO master.