Some common functionality that isn't specific to any particular project.

			Versioning
  The header version can be found examining the _XF_*_H definition,
which defines comma separated version numbers. The format is:
"major,minor,revision", without the quotes of course.

  New versions, unless major number is iterated, should always work
with previous implementations.

			Object orientation (since 0.2b)
  When an object(struct) has a bunch of variables that needn't be on
dynamically allocated memory, their lifetime functions are:
	(struct xf_X *) xf_X_construct(struct xf_X *x [, ...]);
	(void) xf_X_destruct(struct xf_X *x [, ...]);

  If the main-structure is more convinient in malloc'ed variable
sized memory, the functions will allocate the instance for you:
	(struct xf_X *) xf_X_create([...]);
	(void) xf_X_destroy(struct xf_X *x);

  Note that if both lifetime function types are given, don't use
them interchangably.

  Explanation: the _construct/_destruct is supposed to imply that
they're subclass'es (possibly part of a superclass(struct)).
_create/_destroy could be class reference.
  Generally _create/_destroy add an additional indirection with pointers.
  This naming convention carefully avoided using _alloc and _free, which
for memory models may conflict with other functionality.

			General macros
  Some macros are defined for all libraries. Distinguishing them
from header-specific input macros is prefix '_'. These will not be
defined nor undefined in the header/source units.
  List follows:
_XF_STATIC		Whether or not to include function bodies. Defaults
	to value «1».
_XF_FNC_FLAGS		The flags which are prepended to function
	definitions. If macro is undefined and _XF_STATIC is 1(or undef),
	then default is «static inline». If _XF_STATIC is defined and 0,
	then this defaults to «»(empty def).

  And some other macros:
_XF_MACROS		Used internally when .c is included before .h
	(expected functions to be linked instead of statically included)
	to retrieve the internal "local" definitions.
_XF_*_H			Versioning macro as explained above at "Versioning".