doc: compilation: Add libtiff to additional deps

Signed-off-by: Cyril Hrubis <metan@ucw.cz>
loaders: ByteUtils: Correct comments in header.

The comments in the header were wrongly defining
the return value as a number of bytes instead of
number of sucesful conversions.

Signed-off-by: Cyril Hrubis <metan@ucw.cz>
loaders: Add image containers + ZIP container.

Image container is an abstraction for image formats capable of storing
several images. The container could be opened and image loaded one by
one.

ZIP container is first container implementation, it can load images from
a ZIP file, so far it can only handle JPEGs and deflate compressed ZIPs.
This is also base code for implementing CBZ support for spiv.

Signed-off-by: Cyril Hrubis <metan@ucw.cz>
core: Fix typon in GP_Threads.h

Signed-off-by: Cyril Hrubis <metan@ucw.cz>
spiv: Small cleanup.

Signed-off-by: Cyril Hrubis <metan@ucw.cz>