New in 5.18.3 - May 2014

* ATTRIBUTE_FORMAT_ARG is a configured attribute that wraps
  __attribute__((__format_arg__(n))) procedure declaration attributes.
  To configure it, the ag_macros.m4 has a new macroo,
  AG_COMPILE_FORMAT_ARG (which is a compile only test probe).

* Auto-edit Guile headers that depend upon configure values
  most especially:  noreturn
  but check for "ptrdiff_t" in our configure too, so that Guile does
  not create its own duplicate definition.

* Abort from the failing function so that stack traces are useful
* The libopts m4 configure code must configure the libopts/Makefile
* Happy 2014 New Year
* make sure library option handling code does nothing when the
  library is just trying to get information about an option.
* Only apply texi2mdoc when it is needed.
* The aoGetsText() emitted i18n helper function needs its argument
  to have the "format_arg" attribute.

New in 5.18.2 October 2013

* documentation clarifications
* properly create generated main procedures from user supplied code.
* ChangeLog files have been removed from GIT sources
  (though still obtainable with tagged checkouts).
* LIBGUILE_PATH is not needed and its derivation is wrong on
  where binaries and libraries have different prefixes.

New in 5.18.1 September 2013

* fixed char casting issue that shows in UTF-8 files
* fixed installation error for str2init
* fixed failure handling in the usage template
* fix broken flag values for auto-supported options
* various tweaks to make Coverity happy.
* allow the fatal error message functions to be tagged "noreturn"
  and incorporate sysnoreturn.h technology into AutoGen.

New in 5.17.4 May 2013

* --save-opts documentation cleanup
* optionMemberList() will return an allocated string containing
  the names of the bits set in the option.
* tab stripped "here strings" include stripping the backslash
  escape character when it precedes any whitespace character.
