memleak bugfix + cleanup + Makefile

Closed anthraxx requested to merge (removed):master into master
  • memleak bugfix as free() was missing
  • dont call malloc() manually (the old way getline() always called realloc() anyway because of the way the malloc() was written [did not allocate enought memory for the string])
  • small minor cleanup
  • adding simple Makefile to build door challenge

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