Clean up the parts of configure.in responsible for handling libidn2
detection and adjust other pieces of the build system to match these
cleanups:
- use pkg-config when --with-libidn2 is used without an explicit path,
- look for idn2_to_ascii_lz() rather than idn2_to_ascii_8z() as the
former is used in BIND while the latter is not,
- do not look for idn2_to_unicode_8zlz() as it is present in all
libidn2 versions which have idn2_to_ascii_lz(),
- check whether the <idn2.h> header is usable,
- set LDFLAGS in the Makefile for dig so that, if specified, the
requested libidn2 path is used when linking with libidn2,
- override CPPFLAGS when looking for libidn2 components so that the
configure script does not produce warnings when libidn2 is not
installed system-wide,
- merge the AS_CASE() call into the AS_IF() call below it to simplify
code,
- indicate the default value of --with-libidn2 in "./configure --help"
output,
- use $with_libidn2 rather than $use_libidn2 to better match the name
of the configure script argument,
- stop differentiating between IDN "in" and "out" support, i.e. make
dig either support libidn2 or not; remove WITH_* Autoconf macros and
use a new one, HAVE_LIBIDN2, to determine whether libidn2 support
should be enabled.
a0571d3851