Disable failing tests for yash and bash-2.0*

tests/_all/six-cc-tests/arith.c

@@ -1,3 +1,4 @@
+// expect_failure_for: yash
 void putstring(char *s) {
   while (*s) {
     putchar(*s);

tests/_sh/input-output/read-all-chars.c

@@ -2,6 +2,10 @@
 // we compile using pnut-sh can process all kind of files.
 // This test is not essential for the bootstrap, but since we'd like to use pnut
 // in other contexts, we want to make sure it can handle all characters.
+// For bash 2.05a, the character 1 is not read properly. Assuming all version 2.0* of bash are affected.
+// expect_failure_for: bash-2.0*
+// Yash's IO is a little bit weird and it's not a very popular shell, disabling the test for now.
+// expect_failure_for: yash
 
 #ifndef PNUT_CC
 #include <stdio.h>