Add Feature History to doc. Update common extensions.
Merge branch 'gawk-4.1-stable'
Update copyright year in configure.ac field.c.
Sync pc/Makefile.tst with mainline test/Makefile.am.
Merge branch 'gawk-4.1-stable'
Add expected failure warnings in pc/Makefile.tst.
Merge branch 'gawk-4.1-stable'
Update to latest texinfo.tex.
Merge branch 'gawk-4.1-stable'
Next tarball, bumps version.
Merge branch 'gawk-4.1-stable'
Fix the test suite for the pc ports.

test/strftime.awk: If DATECMD variable is non-empty, use it instead
of the literal "date" as the 'date'-like command.

pc/Makefile.tst (strftime): Pass the value of 'date' command
through the DATECMD variable.
(readdir): Adapt to changes in test/readdir0.awk.
Fix bug that only showed up on 32 bit systems with MPFR.
Sync dfa.c with GNU grep.
Merge branch 'gawk-4.1-stable'
Update doc for Anders Wallin.
Merge branch 'gawk-4.1-stable'