FastR grid: implement L_textBounds

...com/oracle/truffle/r/library/fastrGrid/EdgeDetection.java

...src/com/oracle/truffle/r/library/fastrGrid/GridState.java

.../com/oracle/truffle/r/library/fastrGrid/GridTextNode.java

...src/com/oracle/truffle/r/library/fastrGrid/GridUtils.java

...ary/src/com/oracle/truffle/r/library/fastrGrid/LText.java

...c/com/oracle/truffle/r/library/fastrGrid/LTextBounds.java

...m/oracle/truffle/r/library/fastrGrid/TransformMatrix.java

.../nodes/builtin/base/foreign/CallAndExternalFunctions.java

mx.fastr/copyrights/overrides