Fallbacks for IDN library detection
Fallbacks for IDN library detection

When not explictly given --enable-runtime/--enable-builtin,
./configure tries to first detect libidn2, then libicu, then
libidn. If none found, it fals back to --disable-runtime and
--disable-builtin.

Reported-by: Chun-wei Fan

rockdaboot/libpsl,dago/libpsl,dago/libpsl,rockdaboot/libpsl,dago/libpsl,rockdaboot/libpsl