convert images to xpm

Changes since last version:
* whitespace changes
* corrected sanity tests
* changed signature to pass clut and clut_len to function
* updated unit tests for new signature

Kristen Carlson Accardi (2):
stkutil: convert img to xpm
test-stkutil: unit test for img to xpm converter

 src/stkutil.c       |  147 ++++++++++++++++++++++++++++++
 src/stkutil.h       |    9 ++
 unit/test-stkutil.c |  247 +++++++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 403 insertions(+), 0 deletions(-)