php8: Support for icu 75

php8: Support for icu 75

Preparing to update icu4c to 75.
Created a patch for build errors in php-intl.
```
In file included from /mnt/node/openwrt/staging_dir/target-aarch64_generic_musl/usr/include/unicode/unistr.h:39,
                 from ext/intl/intl_convertcpp.h:22,
                 from ext/intl/intl_convertcpp.cpp:17:
/mnt/node/openwrt/staging_dir/target-aarch64_generic_musl/usr/include/unicode/stringpiece.h:133:29: error: 'enable_if_t' in namespace 'std' does not name a template type
  133 |             typename = std::enable_if_t<
      |                             ^~~~~~~~~~~
/mnt/node/openwrt/staging_dir/target-aarch64_generic_musl/usr/include/unicode/stringpiece.h:133:24: note: 'std::enable_if_t' is only available from C++14 onwards
  133 |             typename = std::enable_if_t<
      |                        ^~~
/mnt/node/openwrt/staging_dir/target-aarch64_generic_musl/usr/include/unicode/stringpiece.h:133:40: error: expected '>' before '<' token
  133 |             typename = std::enable_if_t<
      |                                        ^
```
The FreeBSD ports patch was used as a reference.
https://github.com/freebsd/freebsd-ports/commit/e680bd98d34a86302db434c5be23d0cf9d23df23

Signed-off-by: Hirokazu MORIKAWA <morikw2@gmail.com>