Log Message:
Update to 0.31.0

  Fix in MKC_CHECK_PROTOTYPES.  The problem was it says "found" for
  undeclared prototypes.

  All FEATURES now check for _MKC_CHECK_<xxx> define.  A check for
  this define guarantees that #include <mkc_XXX.h> are not used
  without appropriate MKC_FEATURES += <xxx> in Makefile.

  New publicly available mkc.conf.mk header was introduced.  With a
  help of it one can implement custom "FEATURES".

  MKC_CHECK_HEADERS, MKC_CHECK_HEADER_FILES, MKC_CHECK_DEFINES,
  MKC_CHECK_TYPES, MKC_CHECK_VARS, MKC_CHECK_MEMBERS,
  MKC_CHECK_FUNCS<n>, MKC_CHECK_PROTOTYPES, MKC_CHECK_SIZEOF and
  MKC_PROTOTYPE_HEADERS.<name> now accepts a list of comma-separated
  headers for checking at once.
  For example, on NetBSD sys/fts.h requires preceding sys/types.h and
  sys/stat.h. So, now we can write
     MKC_CHECK_HEADERS  = sys/types.h,sys/stat.h,fts.h

  MKC_CHECK_FUNCS<n>: new variable MKC_FUNC_OR_DEFINE.<func> was \ 
introduced.
  With a help of it one can check for
  function declaration of equivalent define.

  mkc_imp.conf-final.mk: duplicated entries are not added to CPPFLAGS,
  CFLAGS, LDADD and SRCS.

  Man page for mkc_check_decl, mkc_check_sizeof and mkc_check_headers
  were updated.

  mkc.minitest.mk: new variable MKC_DIFF was introduced for diff(1)
  command.

  mkc_check_decl: new check type funcordefine was introduced.

  Improvements and minor fixes in regression tests and examples.

  This release was sucessfully tested on FreeBSD-11.1, diverse
  glibc-based Linuxes, NetBSD-8.99, OpenBSD-6.4 and SunOS-5.11.

  Deprecated features were removed: DPLIBS and PKG_CONFIG_DEPS variables,
  builtin "endianess".