change the name for the generated keyword tests to make them unambigous

the problem was the ALL keyword which caused a naming conflict with
Opm::ParserItemSizeEnum::ALL. I haven't considered the possibility to
break the build by adding a keyword, so sorry for the breakage.

On a more philosophical ground I think it is a bit questionable to
auto-generate test cases at build time because they will automatically
match the keyword definition, whether this definition makes sense or
not...
add the ALL keyword

The documentation of this keyword is quite well hidden in the "Other
SUMMARY keywords" section of the Eclipse reference manual, but the
keyword itself seems to be widely used...
Merge pull request #325 from andlaus/add_ALL_v2

Add the ALL keyword (v2)