Description:
------------
I've noticed that recently I've been getting tons of warnings compiling PHP, which are the same warning essentially:

/src/php-src/Zend/zend_API.c:333:21: warning: implicit conversion from 'long' to 'double' changes value from 9223372036854775807 to 9223372036854775808 [-Wimplicit-int-float-conversion]
                                if (UNEXPECTED(!ZEND_DOUBLE_FITS_LONG(d))) {
                                                ^~~~~~~~~~~~~~~~~~~~~~~~
Zend/zend_operators.h:93:45: note: expanded from macro 'ZEND_DOUBLE_FITS_LONG'
#       define ZEND_DOUBLE_FITS_LONG(d) (!((d) >= ZEND_LONG_MAX || (d) < ZEND_LONG_MIN))
                                               ~~ ^~~~~~~~~~~~~
Zend/zend_long.h:34:24: note: expanded from macro 'ZEND_LONG_MAX'
# define ZEND_LONG_MAX INT64_MAX
                       ^~~~~~~~~
/usr/include/stdint.h:163:22: note: expanded from macro 'INT64_MAX'
# define INT64_MAX              (__INT64_C(9223372036854775807))
                                 ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/usr/include/stdint.h:145:24: note: expanded from macro '__INT64_C'
#  define __INT64_C(c)  c ## L
                        ^~~~~~
<scratch space>:32:1: note: expanded from here
9223372036854775807L
^~~~~~~~~~~~~~~~~~~~
Zend/zend_portability.h:323:52: note: expanded from macro 'UNEXPECTED'
# define UNEXPECTED(condition) __builtin_expect(!!(condition), 0)
                                                   ^~~~~~~~~

This seems to have something to do with how we do ZEND_DOUBLE_FITS_LONG and it's extremely annoying and makes it hard to watch for other warnings. 

The compiler is standard one coming with macOS Mojave:

Apple LLVM version 10.0.1 (clang-1001.0.46.4)
Target: x86_64-apple-darwin18.7.0

but other clang versions, like on Linux:
clang version 10.0.0 (trunk 371202)

produce the same.