Adding cummin and cummax as builtins.

...s/src/com/oracle/truffle/r/nodes/builtin/base/CumMax.java

...s/src/com/oracle/truffle/r/nodes/builtin/base/CumMin.java

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

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

...le.r.test/src/com/oracle/truffle/r/test/all/AllTests.java

.../com/oracle/truffle/r/test/simple/TestSimpleBuiltins.java

mx.fastr/copyrights/overrides