[patch] expr.c: Fix formatting.

[Andrew Haley]

Surely this is wrong:

-  /* c contains character after number. */
-  /* input_line_pointer->char after c. */
+  /* C contains character after number.  */
+  /* INPUT_LINE_POINTER -> char after C.  */
   small = (input_line_pointer - start - 1) < too_many_digits;
 
Tha variable is called "c", not "C".

Andrew.