Looking for source code on my compiler's rand() function for C

I am using the latest MINGW compiler and I want to know if its possible to see the source code for my rand() function from stdlib.h. The purpose is I want to hack the PRNG for a password-cracking networking project (just for fun; I could easily brute-force it). I am hoping to get the multiplier and addend from the function or to see how the seed is implemented.

I've already been to: http://ift.tt/NiWZZS

and downloaded the .xz file, the .gz file and used 7zip to open them. I found some functions but the .c file for rand() is nowhere to be seen. I've been into every single file in both and I have found neither anything to do with stdlib.h or rand().

How am I supposed to navigate these libraries to look for what I want? Is there a tutorial or a book I can read to help me for this purpose? (I've already ordered http://ift.tt/2fIpzpg but I don't know whats in it yet)