5.2.0

This release contains a number of fixes and improvements, and one new feature, which is a method for IsSelfDualSemigroup and related functionality for semigroups satisfying CanUseFroidurePin:

• m4/find_gap.m4: update by @fingolfin in #887
• Adds method for IsSelfDualSemigroup and related functionality by @james-d-mitchell in #890
• Fix some bugs by @james-d-mitchell in #889
• Fix closure semigroup for non-libsemigroups types by @james-d-mitchell in #891
• Add missing tests and doc for IsSelfDualSemigroup and friends by @james-d-mitchell in #892
• Change -march=avx -> -mavx by @james-d-mitchell in #896
• Fix faulty usage of 0-simple RZMS translations code by @flsmith in #893
• build: replace m4/ax_check_hpcombi by @james-d-mitchell in #897