log4cxx-0.11.0-bp156.3.4

- update to 0.11.0:
  * maintenance release, see https://logging.apache.org/log4cxx/latest_stable/changes-report.html#a0.11.0
- drop gcc6.patch, log4cxx-fix_duplicate_entries.patch: obsolete

- fix license to SPDX form

- Fix build with GCC6. gcc6.patch.
  https://issues.apache.org/jira/browse/LOGCXX-463

- Remove redundant sections (cf. specfile guidelines)

- Fixed building on openSUSE:Factory
- Cleaned up spec file formatting
- Moved to .changes file
- Added pkg-config buildrequires (fix for RMPLINT warning)
- Changed license naming to conform to SPDX convention (fix for RMPLINT warning)
- Fixed group (fix for RMPLINT warning)

- Fixed broken builds