[Composer] Filter out platform packages

[binary-data]

Hi! Currently confused outputs "ext-*" as unsafe packages. You may probably want to filter them out. You may want to check "lib-*" prefix or "hhvm" as well: https://getcomposer.org/doc/01-basic-usage.md#platform-packages

Example output:

Issues found, the following packages are not available in public package repositories:
 [!] ext-readline
 [!] ext-zip
 [!] ext-redis
 [!] ext-mongodb
 [!] ext-zlib
 [!] ext-mysqli
 [!] ext-json
 [!] ext-curl
 [!] ext-libxml
 [!] ext-zend-opcache
 [!] ext-amqp
 [!] ext-iconv
 [!] ext-simplexml
 [!] ext-ast
 [!] ext-openssl
 [!] ext-apcu
 [!] ext-pdo
 [!] ext-calendar

[joohoi]

Thanks for opening the issue! I'll dig into this a bit more and figure out the proper action. I'll have to make sure that these are not claimable in the Composer repositories (which I assume is the case) etc.