Check for strcpy_s() and strcat_s() at configure time

It is better to test for functions than to hardcode exceptions for
specific compilers.

This fixes compiling poppler with the latest mingw-w64 compiler which
has strcpy_s() and strcat_s() build in.

Bug #63459
Splash: Always consider a softmask transfer function

Fixes bug 63587 in splash
cairo: Always use the trasnfer function if present in setSoftMask

"If the subtype is Alpha, the transparency group XObject G shall be
evaluated to compute a group alpha only. The colours of the constituent
objects shall be ignored and the colour compositing computations shall
not be performed. The transfer function TR shall then be applied to the
computed group alpha to produce the mask values."

We were using the transfer function only for luminosity soft masks.

https://bugs.freedesktop.org/show_bug.cgi?id=63587
Make sure getKids returns != 0 before using it

Fixes crash in bug #63909
Do not start drawing a form we are already drawing

Bug #63190
Update my C of the last two previous commits
We need UnicodeParsedString here too

Fixes KDE bug #307786
Fix compilation with fixed point mode enabled

Thanks to Andreas Müller for the tip
Update copyright years
0.22.4 NEWS
0.22.4 version

Also increase soversion since Gfx.h got a new member