Getting rid of ksh in the IOISPL install scripts

[emillour]

On some systems ksh is not installed as bash is the default.
However the IOIPSL installation scripts (the ones included in the IOIPSL distribution, not the ones in LMDZ.COMMON/ioipsl which download IOIPSL and attempts to build it) are in ksh.
It would be convenient to explicitly handle the case, either by checking if ksh is available and if not modifying the scripts to be in bash. Or simply always doing that change without even checking if ksh is available.

[emillour]

In practice one only need to do a

sed -i -e s:'/bin/ksh':"/bin/bash":1 ins_m_prec

in the IOIPSL directory
see e.g. r2798

[emillour]

Done in r2811 for some "general" install scripts