Fix EOF == -1 assumption in 1994/shapiro

The problem is that the getc() functions return EOF on error/EOF but it
assumed that it returns -1. EOF is not required to be -1 but merely an
int < 0 so on systems where it was not -1 it could be a problem. But
changing the != -1 check to be != EOF caused a new compiler warning and
errors. However since EOF < 0 and since the code functions fine with the
check being >= 0 the code now checks that the return value of getc() >= 0
as the condition of the for loop. This takes care of any problem where
EOF != -1.

Fixed accidental change in shapiro.md code excerpt. Note that that one
(the first one) does not actually work but it never did (or if it did it
doesn't in modern systems). I'm not sure this is a problem though as the
author stated that without the comments the program will not do anything
right. I believe the author was showing the algorithm without comments.

1994/shapiro/shapiro.c

@@ -11,7 +11,7 @@
           /*T*/,"r");for      (;(       L/*KPUOWOWMUQ
          LLOLMPULWLWL         WLW         LWLWLWLWLWLW
          LWLWLULVOXP          LLV          LLLOLMPULOL
-        MMNP*/=getc           (J)            )!= -1;L/*
+        MMNP*/=getc           (J)            )>= 0;L/*
        OLWLRMMQUL             VOX             PLLVLLLMQO
        PMPYPXPNP              MQL              LVLLLWPSP
       XPOQNQOPMQ              LLV              LTj*/>='J'