Compilation issues with ICU 68

[lecoredump]

Hello, and first of all, thanks for the work done so far.

There seems to be no possibility to build using asdf-php when ICU is v68 or above. Indeed, as stated here http://site.icu-project.org/download/68, the v68 ICU library doesn't define TRUE and FALSE, which results in the following issue (regardless of minor version installed, the 7.{0-2} cannot build), example for 7.1.33) :

/tmp/tmp.JS3ZQ5bJJH/php-src-php-7.1.33/ext/intl/timezone/timezone_class.cpp: In function ‘HashTable* TimeZone_get_debug_info(zval*, int*)’:
/tmp/tmp.JS3ZQ5bJJH/php-src-php-7.1.33/ext/intl/timezone/timezone_class.cpp:324:28: error: ‘FALSE’ was not declared in this scope
  324 |         tz->getOffset(now, FALSE, rawOffset, dstOffset, uec);
      |                            ^~~~~
make: *** [Makefile:1244: ext/intl/timezone/timezone_class.lo] Error 1
make: *** Waiting for unfinished jobs....
/tmp/tmp.JS3ZQ5bJJH/php-src-php-7.1.33/ext/intl/timezone/timezone_methods.cpp: In function ‘void zif_intltz_from_date_time_zone(zend_execute_data*, zval*)’:
/tmp/tmp.JS3ZQ5bJJH/php-src-php-7.1.33/ext/intl/timezone/timezone_methods.cpp:94:64: error: ‘FALSE’ was not declared in this scope
   94 |         tz = timezone_convert_datetimezone(tzobj->type, tzobj, FALSE, NULL,
      |                                                                ^~~~~
make: *** [Makefile:1246: ext/intl/timezone/timezone_methods.lo] Error 1

From what I could gather, the a "temporary" way to fix this would be to define the U_DEFINE_FALSE_AND_TRUE to 1 for gcc not to error at compile time, but I don't really know where or how it would fit with the rest of the existing code (in asdf-php), or if it even should be considered.

Any ideas / suggestions ?