Fix 2006/sloane for clang

The problem was that the second arg was not of type char ** but an
implicit int and broken record though I am clang forces the types to be
correct without any option to disable this.

As it happens though the second arg is not even used so I removed it as
clang does allow this for some reason. This helps with keeping the
original format as close as possible. This triggers a different warning
but that's okay.

I also added a warning to the README.md about how it is a lot of change
in text very quickly as this could cause some problems for some people.

2006/sloane/sloane.c

@@ -13,7 +13,7 @@ KXw{Y"   "RsFwsFwsFw{zaqyaz|FmMpyaoyI\\]cuUw{J"
        "~|_."[c(6,"b"              "cd\\a[g","^`"   "_e"
        "]fh")+8], p(   "#$%"        "&'()*+,-.1"[   c(11
       ,"_ac[]\\YZi"   "jkm",         "`bd^efghXWlV" )+13
-      ]-34,a);}main   (k,Z){         float z[1920]  ,A=0
+      ]-34,a);}main   (k  ){         float z[1920]  ,A=0
 ,B=0  ,i,j; puts(""         "\x1b"   "[2J");for(;;
 )  {  float e=sin(A         ),  n=   sin(B),g=cos(
 A),m   =cos(B);for(k        =0;k<   1840;k++)y=-k