tools/make: build with -Wno-deprecated-declarationsUse NB_CHECK_CC_FLAG() from ../tools/compat to determineif the compiler supports -Wno-deprecated-declarations.Avoids sooking about vfork() on macOS.
branches: 1.1.2;* Add Makefile.regen to regenerate configure from configure.ac;* Add comments in configure.ac to explain how to regenerate configure.