#9 Make it easy to build tkimg with the system libraries

[Sergio Pascual]

Currently, tkimg builds with its own versions of libpng, libjpg, etc. This is a problem when building packages for fedora linux (and probably other linux distributions) because linking with custom versions of libraries is usually a bad idea[1]

Thus, it would be great to have configure switches to allow building with the system libraries

[1] http://fedoraproject.org/wiki/Packaging/Guidelines#Duplication_of_system_libraries

[Sergio Pascual]

With the exception of the tiff driver, tkimg can use external libraries fairly easily.

The tiff driver can't be compiled using the system headers only. I suppose that this means that tifftcl is using internals of the tiff library.

[Sergio Pascual]

The png driver uses some deprecated interface of the png library. The functions png_read_destroy and png_write_destroy are deprecated and aren't exported by the dynamic library png12.so
Removing these two functions from tkimg would make it more compatible with external libraries