VSEARCH 2.29.3

This version is released in order to mitigate a bug that occurs when compiling the align_simd.cc file on x86_64 systems with the GNU C++ compiler version 9 or later with the -O3 optimization option. It results in incorrect code that may cause bad alignments in some circumstances. So far it has only been seen with the allpairs_global command. We are investigating this issue further, but for now we recommend compiling with the -O2 flag. The README.md file and the Dockerfiles have been updated to reflect this. The binaries released with this version will include this fix.