Optimize pack()

Instead of using lookup tables, we can use a combination of shifts and
byte swapping to achieve the same thing in less cycles and with less
code.

Benchmark files
---------------

pack1.php:
```php
for ($i = 0; $i < 10_000_000; ++$i) {
    pack("J", 0x7FFFFFFFFFFFFFFF);
}
```

pack2.php:
```php
for ($i = 0; $i < 4000000; ++$i) {
    pack("nvc*", 0x1234, 0x5678, 65, 66);
}
```

On an i7-4790:
```
Benchmark 1: ./sapi/cli/php pack1.php
  Time (mean ± σ):     408.8 ms ±   3.4 ms    [User: 406.1 ms, System: 1.6 ms]
  Range (min … max):   403.6 ms … 413.6 ms    10 runs

Benchmark 2: ./sapi/cli/php_old pack1.php
  Time (mean ± σ):     451.7 ms ±   7.7 ms    [User: 448.5 ms, System: 2.0 ms]
  Range (min … max):   442.8 ms … 461.2 ms    10 runs

Summary
  ./sapi/cli/php pack1.php ran
    1.11 ± 0.02 times faster than ./sapi/cli/php_old pack1.php

Benchmark 1: ./sapi/cli/php pack2.php
  Time (mean ± σ):     239.3 ms ±   6.0 ms    [User: 236.2 ms, System: 2.3 ms]
  Range (min … max):   233.2 ms … 256.8 ms    12 runs

Benchmark 2: ./sapi/cli/php_old pack2.php
  Time (mean ± σ):     271.9 ms ±   3.3 ms    [User: 269.7 ms, System: 1.3 ms]
  Range (min … max):   267.4 ms … 279.0 ms    11 runs

Summary
  ./sapi/cli/php pack2.php ran
    1.14 ± 0.03 times faster than ./sapi/cli/php_old pack2.php
```

On an i7-1185G7:
```
Benchmark 1: ./sapi/cli/php pack1.php
  Time (mean ± σ):     263.7 ms ±   1.8 ms    [User: 262.6 ms, System: 0.9 ms]
  Range (min … max):   261.5 ms … 268.2 ms    11 runs

Benchmark 2: ./sapi/cli/php_old pack1.php
  Time (mean ± σ):     303.3 ms ±   6.5 ms    [User: 300.7 ms, System: 2.3 ms]
  Range (min … max):   297.4 ms … 318.1 ms    10 runs

Summary
  ./sapi/cli/php pack1.php ran
    1.15 ± 0.03 times faster than ./sapi/cli/php_old pack1.php

Benchmark 1: ./sapi/cli/php pack2.php
  Time (mean ± σ):     156.7 ms ±   2.9 ms    [User: 154.7 ms, System: 1.7 ms]
  Range (min … max):   151.6 ms … 164.7 ms    19 runs

Benchmark 2: ./sapi/cli/php_old pack2.php
  Time (mean ± σ):     174.6 ms ±   3.3 ms    [User: 171.9 ms, System: 2.3 ms]
  Range (min … max):   170.7 ms … 180.4 ms    17 runs

Summary
  ./sapi/cli/php pack2.php ran
    1.11 ± 0.03 times faster than ./sapi/cli/php_old pack2.php
```

Closes GH-18524.

Co-authored-by: divinity76 <divinity76@gmail.com>

ext/standard/basic_functions.c

@@ -299,7 +299,6 @@ PHP_MINIT_FUNCTION(basic) /* {{{ */
 
 	BASIC_MINIT_SUBMODULE(var)
 	BASIC_MINIT_SUBMODULE(file)
-	BASIC_MINIT_SUBMODULE(pack)
 	BASIC_MINIT_SUBMODULE(browscap)
 	BASIC_MINIT_SUBMODULE(standard_filters)
 	BASIC_MINIT_SUBMODULE(user_filters)