workaround for RT #100847: use IO::Scalar

With new test script tiff_segfault.t and a test image causing the
segfault.
preparing 1.36_51
inc VERSION
MANIFEST update
travis-ci: test with optional dependencies
tiff processing: warn and stop on unrecognised fieldtype

If an unrecognized fieldtype is encountered in a tiff file, then
processing of the file is stopped (previously it was skipped) and a
Warn key is added to the returned info hash.

This should handle the test image from RT #100847.