buildroot

imagemagick: security bump to version 7.0.3-3

Fixes:
memory allocate failure in AcquireQuantumPixels (quantum.c)
heap-based buffer overflow in IsPixelMonochrome (pixel-accessor.h)

No CVEs assigned yet.

Signed-off-by: Gustavo Zacarias <gustavo@zacarias.com.ar>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>