Make USES=php feel like a USES.

[mat]

Summary

• USE_PHPIZE → USES=php:phpize
• USE_PHPEXT → USES=php:ext
• USE_ZENDEXT → USES=php:zend
• USE_PHP_BUILD → USES=php:build
• WANT_PHP_CLI → USES=php:cli
• WANT_PHP_CGI → USES=php:cgi
• WANT_PHP_MOD → USES=php:mod
• WANT_PHP_WEB → USES=php:web
• WANT_PHP_EMB → USES=php:embed

[mat]

• Now, USE_PHP can be empty.

[mat]

• The mhash extension has been removed six years ago, time to let it
• Convert all USE_PHP=yes

[mat]

Fix stuff.

[antoine]

I don't like this change:
it's easier to add stuff to USE_PHP or to use option helpers with USE_PHP than with USES=php

[antoine]

And now I see that it doesn't replace USE_PHP.

[mat]

Rebase.

[mat]

• I hate make(1).