test/driver: Add Valgrind suppressions for g_type_init() leaks
hamamatsu: Reject NDPI slides with suspicious extra levels

Since we don't know how to recognize and ignore levels belonging to
additional focal planes, reject slides that seem to have them.
jp2k: Use precomputed tables in YCbCr-RGB conversion

It provides a modest performance improvement.
Silence spurious gcc longjmp clobber warnings

gcc -Wclobbered is useful but buggy.  Do minimal mangling to avoid the
current crop of spurious warnings.
test/try_open: Fix missing initializer warning
png: Fix build with libpng < 1.5
cache: Fix pointer/int cast warning on 32-bit
tiff: Simplify ARGB conversion

to a bswap and a rotate.