If a hex literal has an 'd' of 'f' in it, such as '0xf' or '0xd', the compiler fails with illegal tree structure.

The other hex literals work.  The issue is probably related to using `f` and `d` in float and double literals.

```
    public void testHexCollisionDouble() {
        assertEquals(13, exec("return 0xd"));
    }

    public void testHexCollisionFloat() {
        assertEquals(15, exec("return 0xf"));
    }

    public void testHex() throws Exception {
        for (int i = 0; i <= 15; i++) {
            String hex = Integer.toHexString(i);
            if ("d".equals(hex) || "f".equals(hex)) {
                continue;
            }
            assertEquals(i, exec("return 0x" + hex));
            assertEquals(i, exec("return 0x" + hex.toUpperCase(Locale.ROOT)));
            assertEquals(i, exec("return 0X" + hex));
            assertEquals(i, exec("return 0X" + hex.toUpperCase(Locale.ROOT)));
        }
    }
```
modules/lang-painless/src/main/java/org/elasticsearch/painless/phase/DefaultSemanticAnalysisPhase.java
* Visits a call local expression which is a method call with no qualifier (prefix).
     * Checks: type validation, method resolution
     */
    @Override
    public void visitCallLocal(ECallLocal userCallLocalNode, SemanticScope semanticScope) {
        String methodName = userCallLocalNode.getMethodName();
        List<AExpression> userArgumentNodes = userCallLocalNode.getArgumentNodes();
        int userArgumentsSize = userArgumentNodes.size();
        if (semanticScope.getCondition(userCallLocalNode, Write.class)) {
            throw userCallLocalNode.createError(
                new IllegalArgumentException(
                    "invalid assignment: cannot assign a value to function call [" + methodName + "/" + userArgumentsSize + "]"
                )
            );
        }
        ScriptScope scriptScope = semanticScope.getScriptScope();
        FunctionTable.LocalFunction localFunction = null;
        PainlessMethod thisMethod = null;
        PainlessMethod importedMethod = null;
        PainlessClassBinding classBinding = null;
        int classBindingOffset = 0;
        PainlessInstanceBinding instanceBinding = null;
        Class<?> valueType;
        localFunction = scriptScope.getFunctionTable().getFunction(methodName, userArgumentsSize);
        
        if (localFunction != null && localFunction.isInternal()) {
            localFunction = null;
        }
        if (localFunction == null) {
            thisMethod = scriptScope.getPainlessLookup()