This is based on #11487 supporting negative decimal places on number_format.

• Passing an int to number_format will perform formatting the int (zend_long) value without casting it to float (double)
• With negative decimal places it will perform rounding to power of 10 using zend_ulong to be able to round high numbers without integer overflow (e.g. 9223372036854775806 -> 10,000,000,000,000,000,000)
• Use of zend_long for decimals (dec argument) as there is a possible integer overflow with big numbers. This issue still exists on formatting floats but fixing it would be a BC break. (opened a separate PR number_format: prevent integer overflow on big decimal number #11649 )

PS: I'm not a C developer and this is the first time for me handling pointers and malloc ... please review carefully that I haven't done a mistake ending up in crashes :)