Using datatoc.c to make the splash screen blender 2.79 I´ve read this:
https://wiki.blender.org/index.php/Dev:2.4/Doc/How_to/Edit_the_SplashScreen
The page points to a c conversor "datatoc.c"
I´m on Blender 2.79 at the moment, with all the source code downloaded.
I am looking into: blender-git\blender\release\datafiles and I see no datatoc.c

I see a ctodata.py and I cite from the same webpage:
If you do use blender 2.5, than there is a python script (that supports .png files) that does this. Invoke it with:
./datatoc.py splash.png

First: I am using this on the command line on windows 7x64:
ctodata.py splash.png

I get this error:
G:\blender-git\blender\release\datafiles>ctodata.py splash.png
Traceback (most recent call last):
  File "G:\blender-git\blender\release\datafiles\ctodata.py", line 47, in 
    data = [int(v) for v in data]
ValueError: invalid literal for int() with base 10: '\x89PNG'

I don´t know where to get that file "datatoc.c" to run it on the command window. It is not on the source code of blender 2.79 dependencies.
Please help.
While this is still considered off-topic -

You are mixing up two similar names, you want to use datatoc but you are running ctodata.py. The page you read is out of date.

datatoc is a c program built as part of building blender. You can find it's source files in source/blender/datatoc/. When you build blender it will be in the build/bin folder.

Tou make use of a custom splash screen you need to build your own copy of blender, therefore the easiest way is to save your image as release/datafiles/splash.png and let the build process merge it into your blender.