fast and complete protocol buffer implementation

Changes for 0.42_02 - 2023-11-13T12:29:58Z

• Avoid issues with enum vlaues that clash with "special" Perl names (e.g. STDERR, BEGIN, ...)
• Speed up map key encoding
• Fix tests on Perl 5.38 (patch by José Joaquín Atria)
• Avoid double-destruction when using threads (patch by Joey Korkames)