Two of gold testsuite scripts require bash [patch]

[Cary Coutant]

>  I have incorporated John's changes and additional icf test changes
> that missed the "#!/bin/sh". Is this ok to commit ?
>
>        * testsuite/icf_safe_so_test.sh: Add #!/bin/sh to start.
>        Change == to -eq.
>        * testsuite/icf_string_merge_test.sh: Add #!/bin/sh to start.
>        * testsuite/icf_safe_test.sh: Add #!/bin/sh to start.
>        Change == to -eq.
>        * testsuite/icf_sht_rel_addend_test.sh: Add #!/bin/sh to start.
>        * testsuite/icf_preemptible_functions_test.sh: Add #!/bin/sh to start.

I think these changes qualify as "trivial and obvious".

-cary