It's already done.
See admin.sma:
Code:
else if (equali(t_arg, "name") || equali(t_arg, "nick"))
{
idtype = ADMIN_NAME
if (equali(t_arg, "name"))
idtype |= ADMIN_LOOKUP
Code:
/* Checks if two strings equal with case ignoring.
* If len var is set then there are only c chars comapred. */
native equali(const a[],const b[],c=0);
I checked source code for amx x 1.76b.