A macro that should be defined by the user prior to including
the glib.h header.
The definition should be one of the predefined GLib version
This macro defines the earliest version of GLib that the package is required to be able to compile against.
If the compiler is configured to warn about the use of deprecated
functions, then using functions that were deprecated in version
GLIB_VERSION_MIN_REQUIRED or earlier will cause warnings (but
using functions deprecated in later releases will not).