buffered-output-stream: Fix some access after free

The memory pointed to by a GMemoryOutputStream can be realloc'd

https://bugzilla.gnome.org/show_bug.cgi?id=711802
data-output-stream: Fix some access after free

The memory pointed to by a GMemoryOutputStream can be realloc'd

https://bugzilla.gnome.org/show_bug.cgi?id=711802
contexts: Fix memory leak in test

https://bugzilla.gnome.org/show_bug.cgi?id=711802
g-icon: Fix memory leak in test

https://bugzilla.gnome.org/show_bug.cgi?id=711802
gsubprocess: Fix error detection logic in tests

Various tests were depending on local_error being set by a callback
when it could never have been the case. Simplify async error detection
logic in those cases, and fix leak of GError.

https://bugzilla.gnome.org/show_bug.cgi?id=711802
gsubprocess: Fix leaks in tests

https://bugzilla.gnome.org/show_bug.cgi?id=711802
gdbus-connection: Fix use after free in test

https://bugzilla.gnome.org/show_bug.cgi?id=711802
gdbus-connection-slow: Fix leak in tests

https://bugzilla.gnome.org/show_bug.cgi?id=711802
gdbus-connection: Fix leaks in tests

https://bugzilla.gnome.org/show_bug.cgi?id=711802