glib: Don't require GLIB_DOMAIN to be a NUL-terminated string

The length might be passed explicitly in the field instead, and the
string might not have a NUL-terminator as happens for example when
passed from the Rust bindings.

This might lead to out of bounds reads.

Thanks to Sebastian Wiesner for noticing this.

meson.build

@@ -707,6 +707,7 @@ functions = [
   'lstat',
   'mbrtowc',
   'memalign',
+  'memmem',
   'mmap',
   'newlocale',
   'pipe2',