Rnorm converted to the new RandGenerationFunctions system

...acle/truffle/r/library/stats/RandGenerationFunctions.java

...library/src/com/oracle/truffle/r/library/stats/Rnorm.java

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

...acle/truffle/r/test/library/stats/TestExternal_rnorm.java