Problem with bash job control

There seems to be a problem, affecting all architectures, with running "bash" under DynamoRIO:

```
$ echo 'PS1="x> "' > rc
$ bin64/drrun -- bash --rcfile rc
x> echo foo
foo
x> /bin/echo foo
foo

[1]+ Stopped bin64/drrun -- bash --rcfile rc
```

Plain "ls" and "tcsh" work as expected.

Probably a regression from adding interception of all signals for better tool support.

It works with "-no_code_api -no_intercept_all_signals".