xalloc - safe memory allocation
-------------------------------

this module implements malloc and friends + some extensions.
If `__DEBUG__` symbol is defined. The functions will provide extended
debug logic and kills the program (passing 0 as size to malloc for example).

The funtions will at all times kill the program if memory can't be allocated for
some reason, this makes the need for client-code to check for `NULL` pointers returned
by these functions redundant.

functions
~~~~~~~~~

`xmalloc()`::

    Just like malloc, this function allocates a block of memory of 'size' bytes. +
    If compiled with the `__DEBUG__` symbol, the function will not allow zero size

`xmallocz()`::

    Exactly like xmalloc but will initialize the block with zero's.

`xrealloc()`::

    Reallocates a previous allocated block of memory to 'size' bytes. +
    If compiled with the `__DEBUG__` symbol, the function will not allow zero size

`xstrdup()`::

    Allocates and copies the string 's' to a new memory location and returns it to the user. +
    If compiled with the `__DEBUG__` symbol, the function will not allow 's' to be a `NULL` pointer

`xmemdup()`::

    Allocates and copies `len` bytes from `ptr` to a new memory location and returns it to the user. +
    If compiled with the `__DEBUG__` symbol, the function will not allow 'ptr' to be a `NULL` pointer

`xfree()`::

    Free's a previous allocated block (pointed to by 'ptr') that is allocated by xmalloc/malloc. +
    If compiled with the `__DEBUG__` symbol, the function will not allow 'ptr' to be a NULL pointer