Implemented Rf_gammafn and others.

...oracle/truffle/r/ffi/impl/common/JavaUpCallsRFFIImpl.java

...rc/com/oracle/truffle/r/ffi/impl/nodes/FFIUpCallNode.java

...m/oracle/truffle/r/ffi/impl/nodes/RandFunctionsNodes.java

...com/oracle/truffle/r/ffi/impl/upcalls/StdUpCallsRFFI.java

...oracle.truffle.r.native/fficall/src/common/rffi_upcalls.h

...e.truffle.r.native/fficall/src/common/rffi_upcallsindex.h

...racle.truffle.r.native/fficall/src/truffle_common/Rmath.c

...cle/truffle/r/nodes/builtin/base/BaseBesselFunctions.java

...acle/truffle/r/nodes/builtin/base/BaseGammaFunctions.java

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

...oracle/truffle/r/nodes/builtin/base/TrigExpFunctions.java

...in/src/com/oracle/truffle/r/nodes/builtin/base/Trunc.java

.../src/com/oracle/truffle/r/nodes/builtin/InternalNode.java

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

...c/com/oracle/truffle/r/runtime/nmath/BesselFunctions.java

....runtime/src/com/oracle/truffle/r/runtime/nmath/Beta.java

...rc/com/oracle/truffle/r/runtime/nmath/GammaFunctions.java

...src/com/oracle/truffle/r/runtime/nmath/MathConstants.java

...runtime/src/com/oracle/truffle/r/runtime/nmath/RMath.java

...e/src/com/oracle/truffle/r/runtime/nmath/distr/Logis.java