graphics/libpano13: update to 2.9.21

• revert unapproved changes from the 2.9.20 update
  • add new SUITESPARSE option
  • remove superseeded patches

Relevant upstream changes:

• new optional suitesparse dependency for improved geometric optimisation speed
• the test suite is now functional again
• a lot of fixes for potential crashes and safer handling of data
• fix for bigendian architectures
• link with libm if necessary
• various installation location and content fixes

Changelog: https://sourceforge.net/projects/panotools/files/libpano13/libpano13-2.9.21/README.txt
PR: 260819
Submitted by: fuz@fuz.su (maintainer)