3.81
Release GNU make 3.81. Update NEWS docs. Enhance the manual to use automake version.texi, and use the canonical FSF copyright features and statement. Some $(realpath ...) tests won't work on Windows; leave them out The jobserver filedescriptor test might fail if some FDs are reserved, so for now comment out that check.
Extend .SECONDEXPANSION to implicit rules. Final fix for bug #13781.
Numerous updates to tests for issues found on Cygwin and Windows. Revert a fix for $? including non-existent files as it shows a bug in the Linux kernel build. Give them a release to fix this. Add some changes from Eli Z. for Windows changes.
Update the make.1 man page. Use rm -f instead of rm in the test scripts. Fixes bug #15085.
Update the test template. A few fixes in run_make_test(). Rename implicit_prereq_eval to patternrules, to be the start of a suite of tests of pattern rules.