A g_input_stream_read_async() implementation can't call
g_input_stream_read() on itself directly because it will fail because
the pending flag is already set. So fix that by invoking the vmethod
directly rather than calling the wrapper. Likewise with
GMemoryOutputStream.
Add a test to gio/tests/memory-input-stream.c to catch read_async
failures in the future.
==2389== 84 (44 direct, 40 indirect) bytes in 1 blocks are definitely lost in loss record 299 of 315
==2389== at 0x4005BDC: malloc (vg_replace_malloc.c:195)
==2389== by 0x4057094: g_malloc (gmem.c:134)
==2389== by 0x406F2D6: g_slice_alloc (gslice.c:836)
==2389== by 0x406F31B: g_slice_alloc0 (gslice.c:848)
==2389== by 0x413D5BB: g_type_create_instance (gtype.c:1867)
==2389== by 0x412372A: g_object_constructor (gobject.c:1482)
==2389== by 0x4122E1D: g_object_newv (gobject.c:1266)
==2389== by 0x4122B93: g_object_new (gobject.c:1178)
==2389== by 0x41AF54C: g_memory_input_stream_new (gmemoryinputstream.c:199)
==2389== by 0x8048BD1: test_read_chunks (memory-input-stream.c:40)
Bug #628331.
==2389== 59 (24 direct, 35 indirect) bytes in 1 blocks are definitely lost in loss record 290 of 315
==2389== at 0x4005BDC: malloc (vg_replace_malloc.c:195)
==2389== by 0x4057094: g_malloc (gmem.c:134)
==2389== by 0x406F2D6: g_slice_alloc (gslice.c:836)
==2389== by 0x406F31B: g_slice_alloc0 (gslice.c:848)
==2389== by 0x403A8A6: g_error_new_literal (gerror.c:117)
==2389== by 0x403AC31: g_set_error_literal (gerror.c:314)
==2389== by 0x41AFD15: g_memory_input_stream_truncate (gmemoryinputstream.c:517)
==2389== by 0x41BAC0F: g_seekable_truncate (gseekable.c:174)
==2389== by 0x8049595: test_truncate (memory-input-stream.c:123)
Bug #628331.