FAQ addition

Hello

Can “Development runtime” be renamed to “Development libraries” on
libsdl.org? It is a confusing description

I assumed that they were for runtime and compiling programs, due to the
name.
I did not install the Binary runtime as I later found out was required.
(it appeared that they were unrequired from the naming)

This is an FAQ addition I would like to suggest for those unwittingly
enough to encounter the same problem as me.

Q: All SDL programs fail to compile with errors about sin() cos() and
undefined references to files like SDL_dgavideo.lo.

then run ldconfig.

JGA: You need to install Development libraries AS WELL AS Binary runtime.