This is a data type to deal with frequently appending to a string.

When a tag is made known to the Validator, which it already knows, the
old id is returned and nothing is added.
As this has to be checked by iterating over all known tags, a new helper
function is written for both SH_Validator_check_tag and
SH_Validator_register_tag: SH_Validator_get_tag.

Because we want also to test this function, we have to include
validator.c in the test file and override the static keyword by an empty
macro. It isn't possible any more to check for correct overflowdetection
by setting the index to UINT_MAX, because it will be iterated over all
data, thus raising an SIGSEGV when doing so. This is solved by filling
garbage unil UINT_MAX is really reached. As there would be an timeout
and it would fill RAM with around 40 GB of garbage, UINT_MAX is
overriden prior to inclusion of validator.c .

Sometimes variables have to be passed to printf. Those the placeholders
are adjusted. Later this should by solved by a variadic function.

On initialization (of data), the Validator's knowledge is filled with some
common tags. This is of course to be replaced later, by some dynamic handling.

Data takes hold of the appropiate Validator.

Validator serves as an syntax checker, i. e. it can be requested whether
a tag is allowed.

The current page has to be returned, not the last one. This would lead
to permanently wrong page ids, so that later no page is accessible.

Tests are done using check, allowing to integrate the tests into the
Autotools.
Methods that are part of another unit, but are called in this unit
aren't tested as this would interfere with the idea of unittests. This
also applies for purely wrapper functions, where a call is passed to
another unit.

Error handling is done by passing an Error structure as inout parameter
to functions that can fail on runtime predictable. This parameter is
always the last one. Methods, where this is not the case, doesn't have an
error parameter.
When an Error is detected, also an ERROR is passed to the log. Because
this isn't implemented yet, it is replaced by a nop.
The macro EXIT becomes now useless. It was used earlier in case of an
error, to terminate the program in the first place. This behaviour is not
userfriendly, but it can't be decided on the library's side, whether
there is an option to inform the user, something must be cleaned up or
even that recovering is possible at all.
Often these recognized errors are a non-working malloc or an over-/underflow.

Error handling can be ignored by the caller by passing NULL to the Error
parameter. Whether an error had occured, is also always possible to be
determined, by examining the return value. If the error occours in a
function returning a pointer, NULL will be returned. If it returns an value,
a special error value of that type is returned, i.e. PAGE_ERR in
SH_Data_register_page. If the return type would be void, a boolean is returned,
which tells, whether the method has succeeded.
(False means, that an error has occured.)

The error may have occured in an intern method and is passed upwards (the stack).
Internally errors are handled by an enum, but this must be considered an
implementation detail and can be changed in later versions.
It is in the responsibility of the caller to recover gracefully. It has
to be assumed that the requested operation have neither worked, nor
actually took place. Those the operation can be retried (hopefully).

Fragment is the core of SeFHT. (As the name suggests) It represents a
Node inside the DOM and all subsequent Nodes (a Tree).

Pages are hold by Data, CMS passes trough the call(s).

data handels all intern data and serves as a cache between the CMS and
the (R)DBMS.

cms will be the base "object", that performs all neccessary actions.