Add warnings for autogen.sh. Fix AC_CONFIG_SRCDIR.
Update obsolete AC macros.
build: change cdrkit location in build-process.md

The cdrkit.org domain expired.
Thanks to gdm85 on IRC for reporting this.
Merge pull request #4765

e2a98d2 Update obsolete AC macros. (randy-waterhouse)
e543811 Add warnings for autogen.sh. Fix AC_CONFIG_SRCDIR. (randy-waterhouse)