Added test for RError detector.

...acle/truffle/r/test/packages/analyzer/FileTreeWalker.java

.../com/oracle/truffle/r/test/packages/analyzer/PTAMain.java

...le/r/test/packages/analyzer/detectors/RErrorDetector.java

...truffle/r/test/packages/analyzer/dump/AbstractDumper.java

...cle/truffle/r/test/packages/analyzer/dump/HTMLDumper.java

...e/truffle/r/test/packages/analyzer/parser/DiffParser.java

.../test/packages/analyzer/parser/LogFileParseException.java

...ruffle/r/test/packages/analyzer/parser/LogFileParser.java

...le/truffle/r/test/packages/analyzer/test/PatternTest.java

...fle/r/test/packages/analyzer/test/RErrorDetectorTest.java