Typo fix.

From-SVN: r68635

gcc/builtins.c

@@ -243,7 +243,7 @@ get_pointer_alignment (tree exp, unsigned int max_align)
    TREE_STRING_LENGTH is the size of the character array, not the string.
 
    ONLY_VALUE should be non-zero if the result is not going to be emitted
-   into the instruction stream and zero if it si going to be expanded.
+   into the instruction stream and zero if it is going to be expanded.
    E.g. with i++ ? "foo" : "bar", if ONLY_VALUE is non-zero, constant 3
    is returned, otherwise NULL, since
    len = c_strlen (src, 1); if (len) expand_expr (len, ...); would not