Implemented max.col builtin

.../com/oracle/truffle/r/nodes/builtin/base/BasePackage.java

...n/src/com/oracle/truffle/r/nodes/builtin/base/MaxCol.java

.../oracle/truffle/r/runtime/data/model/RAbstractVector.java

...est/src/com/oracle/truffle/r/test/ExpectedTestOutput.test

...om/oracle/truffle/r/test/builtins/TestBuiltin_maxcol.java

mx.fastr/copyrights/gnu_r.core.venables.copyright.star

mx.fastr/copyrights/gnu_r.core.venables.copyright.star.regex

mx.fastr/copyrights/overrides