glib-compile-resources was updated to generate octal byte
representation in a string, but unfortunately this breaks the build
on Visual Studio when the generated string sequence exceeds 65535
characters, which is the imposed limit on Visual Studio compilers.

To make things work on Visual Studio builds and to not slow down things
on other compilers, generate a code path for Visual Studio an array of
octal byte representations, as well as a code path for other compilers
that use the new string representation of octal values, and let the
compiler take the appropriate code path when compiling the
generated code.

Fixes issue #1580.