"index" illegal variable name - Error compiling?

Hello.

I´m starting to use the Intel Galileo board.  I have found an error trying to use the word "index" as a variable name.

For example, I used the sketch named “Smoothing" . It does not work. Because this sketch have and "index" as part of the variables.

Here is a more detailed description about the error:

C:\arduino-1.5.3/hardware/tools/x86/i586-poky-linux-uclibc/usr/include/string.h:322:14: error: previous declaration of 'char* index(const char*, int)

JJMM