Implement rmultinom

...ary/src/com/oracle/truffle/r/library/stats/RMultinom.java

...ruffle/r/nodes/builtin/base/foreign/ForeignFunctions.java

...le.r.runtime/src/com/oracle/truffle/r/runtime/RError.java

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

...fle/r/test/library/stats/TestRandGenerationFunctions.java

...str/copyrights/gnu_r_gentleman_ihaka.copyright.star.regex

mx.fastr/copyrights/overrides