lang/gawk: the port had been updated to version 5.3.0

• Improved compatibility with BWK ("The One True Awk"): CSV file parsing and \u escape sequence
• If PROCINFO["BUFFERPIPE"] exists, then pipe output is buffered
• Drop the use of libsigsegv: the value-add was never very much and it caused problems in some environments
• Note that PMA test currently fails (Terence Kelly's "persistent malloc" experimental feature)

Reported by: portscout