www/logswan: Update to 2.1.11

Change log:

• Bump CMake minimum required version to 2.8.12
• Add SPDX short license identifier in source files
• Use CMAKE_C_STANDARD instead of hardcoding compiler flags
• Switch to using getline(3) instead of fgets(3)
• Call hll_init() after doing getopt() processing

Full changelog: https://github.com/fcambus/logswan/blob/2.1.11/ChangeLog