gcancellable: Free up GPrivate in right cleanup context
gfileinfo: Cleanup memory
giomodule: Cleanup global data
giomodule: Allow overriding source directory gio modules are loaded from

When testing (and valgrinding) we need to have a known set of modules
loaded.
gio/tests: Prevent random gio modules from screwing up these tests
gio/tests: Fix some access after free

The memory pointed to by a GMemoryOutputStream can be realloc'd
contexts: Fix memory leak in test
filter-streams: Cleanup custom classes in test
g-icon: Fix memory leak in test
memcheck: Support suppressions for valgrind target