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
throw userNumericNode.createError(new IllegalArgumentException("not a statement: numeric constant [" + numeric + "] not used"));
        }
        int radix = userNumericNode.getRadix();
        Class<?> valueType;
        Object constant;
        if (numeric.endsWith("d") || numeric.endsWith("D")) {
            if (radix != 10) {
                throw userNumericNode.createError(new IllegalStateException("Illegal tree structure."));
            }
            try {
                constant = Double.parseDouble(numeric.substring(0, numeric.length() - 1));
                valueType = double.class;
            } catch (NumberFormatException exception) {
                throw userNumericNode.createError(new IllegalArgumentException("Invalid double constant [" + numeric + "]."));
            }
        } else if (numeric.endsWith("f") || numeric.endsWith("F")) {
            if (radix != 10) {
                throw userNumericNode.createError(new IllegalStateException("Illegal tree structure."));
            }
            try {
                constant = Float.parseFloat(numeric.substring(0, numeric.length() - 1));
                valueType = float.class;
            } catch (NumberFormatException exception) {
                throw userNumericNode.createError(new IllegalArgumentException("Invalid float constant [" + numeric + "]."));
            }
        } else if (numeric.endsWith("l") || numeric.endsWith("L")) {
            try {
                constant = Long.parseLong(numeric.substring(0, numeric.length() - 1), radix);
                valueType = long.class;
            } catch (NumberFormatException exception) {