error: implicit declaration of function 'strtok_r'

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http://stackoverflow.com – I am a newbie in Linux programming (Linux 3.7.10). I tried to compile a program that I got for github but run in to problems with the error. The main program is from ntop where I downloaded the ndpi (https://svn.ntop.org/svn/ntop/trunk/nDPI/) and that compiled ok. The second part is the kernel mode filter that I got from github (https://github.com/ewildgoose/ndpi-netfilter). First, I could not locate strtok_r function declared in any of the header files. I searched the whole system, is it a prebuild function with in the system?. Please any pointers would be highly appreciated. Thanks. (HowTos)