Change license of all install_test_* scripts, used to test Modules
installation, from GPLv3+ to GPLv2+.
Align this way all files from the Modules project under the GPLv2+
license.
Consent has been obtained from copyright holder to perform such move (I
hold the full copyright for these script files).
Related to #389
Adapt tests of install suite to be able to call module function with no
passed arg if tested command equals to "NOARG".
Also adapt these tests to call module with an empty string argument if
tested command equals to empty string.
Adapt tests of install suite to use ',' character as argument separator
(on same command) for non-pure shell languages (Tcl, Perl, Python, Ruby,
Cmake and R).
Help to distinguish a separator between args from a whitespace within an
arg.
