Opcache idea: Support !is_int($x)

[TysonAndre]

Related to #6 - the BOOL_NOT can be skipped

» ~/php-8.0.0-dev-install/bin/php -d opcache.file_cache= -d opcache.opt_debug_level=0x20000 test.php

$_main: ; (lines=1, args=0, vars=0, tmps=0)
    ; (after optimizer)
    ; /path/to/test.php:1-6
L0 (6):     RETURN int(1)

f1: ; (lines=10, args=2, vars=2, tmps=2)
    ; (after optimizer)
    ; /path/to/test.php:2-5
L0 (2):     CV0($x) = RECV 1
L1 (2):     CV1($y) = RECV 2
L2 (3):     INIT_FCALL 1 96 string("var_export")
L3 (3):     T3 = TYPE_CHECK (long) CV1($y)
L4 (3):     T2 = BOOL_NOT T3
L5 (3):     SEND_VAL T2 1
L6 (3):     DO_ICALL
L7 (4):     T3 = TYPE_CHECK (long) CV1($y)
L8 (4):     T2 = BOOL_NOT T3
L9 (4):     RETURN T2