[PATCH v3 1/5] windowscodecs/tests: Fix tests for CopyBlocks.

[Ziqing Hui]

Using strncmp() to compare pixel data buffer leads to incorrect tests.
Also, we should clear the pixel data buffer before editing and comparing them.

Signed-off-by: Ziqing Hui 
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v3: Merge 2 commits into one.

dlls/windowscodecs/tests/ddsformat.c | 32 +++++++++++++++++++++++-----
 1 file changed, 27 insertions(+), 5 deletions(-)