added a primitive scan line function for standard input

[flysand7]

Function relies on C's fgets. it's behaviour is described as follows: Returns string allocated using allocator with length at max 256 characters.

[flysand7]

.. And the string returned will not include newline.

This function will need to be replaced with something else later though.

[flysand7]

This function returns a line entered by user as a string.

• The length can be arbitrary.
• The newline character isn't included.