Symbols preceded by an underscore are reserved for future introductions
by the c standard/library.

An array index should be of size_t instead of unsigned int.

Internal struct definitions shouldn't be exported by header files.

The validator was used to check that every created tag is validate.
However I now think that validation should take place at a later time,
so it is not mandatory.
Thus developing the validator is now discontinued.

Often it is needed to iterate over the tags. So this was moved to a
macro to reduce code duplication.

Copying a Validator could be useful if multiple html versions are to be
supported. Another use case is a blacklist XSS-Scanner.

A registered tag can be deregistered by calling SH_Validator_deregister.
The data is removed, but the space is not deallocated, if it is not at
the end. This prevents copying data on removal and saves expensive calls
to realloc. Instead the empty space is added to the list of free blocks,
which allows to refill these spaces, if a new tag is being registered.
The space is finally deallocated, if the validator is being deallocated
or the tag written in the last block is removed. In this case, heavy
iteration is performed, as the list of free blocks is not ordered. The
next last tag at that time is determined by iterating over the list of
free blocks until some it is not found.
Note that even if there can be a lot of gaps in between, the Validator
will not allocate more space until all these gaps are refilled when a
new tag is registered, thus new space is only being allocated, if there
is really not enough space left.
Due to the 4 nested loops, there was an issue related to the
72(80)-column rule. It can't be abided without severely impacting the
readability of the code.

Source code regarding tags are exported to validator_tag.c and
validator_tag.h for better separation and integration of new features.

The Validator saves the tags as an array. Now also another information
is added, which slots aren't used currently to spare expensive calls to
realloc. This led to a mere reimplementation of the functions. Tags
can't be deleted by now, but the adding function supports reusing empty
slots. Also the reading functions have to determine, whether a slot can
be read or is empty.
The tests were adjusted, but are buggy, so they should be rewritten in
the future.

Additionaly some annotations for splint were added.

Instead of the trivial structure SH_Error, SH_Status is used. The name
was chosen, because error/status is set independently whether an error
has occurred. Beside the error type, it also contains the associated
errno and an error message. The error message is also printed, when it
is set. Generating error messages with variadic arguments is now also
supported.
There are also macros to check for a set status.

The exception handling was removed for the *_free methods, because they
can't fail predictably during runtime.

Unfortunately the compiler reports, that inside the macro set_status
printf may be called with NULL [printf (NULL)], although, this is
explicitly debarred.

The make process was restructured to create a library. For this libtool
is used to provide both static and dynamic linking. Also header
inclusion guards were introduced, to prevent clients of the library to
include some single file without including others. The types were
exported with forward declarations for better abstraction. When
compiling the library, the macro LIB_SEFHT_COMPILATION is defined and
symbol declarations are exported fully. For compiling the tests this
macro is also defined, as the tests not only tests the API, but also the
internal state, because a lot of errors couldn't be detected otherwise.