glib-compile-resources: Fix size allocation for compressed streams
glib-compile-resources: Fix size allocation for compressed streams

The length of the stolen data from a memory output stream is given by
get_data_size() — get_size() can be larger, and hence cause unnecessary
overallocation.

endlessm/glib,endlessm/glib,endlessm/glib,endlessm/glib,endlessm/glib