Memoize PHP compatibility info
Memoize PHP compatibility info

Summary: Ref T7892. Avoid reading the PHP compatibility information for every file being linted.

Test Plan:
```name=Before
real    1m24.327s
user    1m19.571s
sys 0m5.239s
```

```lang=After
real    1m12.029s
user    1m5.756s
sys 0m5.502s
```

Reviewers: epriestley, #blessed_reviewers

Reviewed By: epriestley, #blessed_reviewers

Subscribers: Korvin, epriestley

Maniphest Tasks: T7892

Differential Revision: https://secure.phabricator.com/D12518

Khan/arcanist,uber/arcanist,KieranHayes/arcanist,memsql/arcanist,wharris/arcanist,hach-que/arcanist,r4nt/arcanist,wxstars/arcanist,alexmv/arcanist,Khan/arcanist,haskell-infra/arcanist,kevinseelbach/arcanist,sneakpeeq/arcanist,wikimedia/phabricator-arcanist,haskell-infra/arcanist,fivestars/arcanist,chundongwang/arcanist,Symplicity/arcanist,jra3/arcanist,memsql/arcanist,phacility/arcanist,wharris/arcanist,memsql/arcanist,coursera/arcanist,PageUpPeopleOrg/arcanist-patches,r4nt/arcanist,aik099/arcanist,Khan/arcanist,sneakpeeq/arcanist,eSpark/arcanist,sneakpeeq/arcanist,r4nt/arcanist,aik099/arcanist,Symplicity/arcanist,hach-que/arcanist,PageUpPeopleOrg/arcanist-patches,kevinseelbach/arcanist,sneakpeeq/arcanist,codelabs-ch/arcanist,phacility/arcanist,jra3/arcanist,jra3/arcanist,coursera/arcanist,zhihu/arcanist,wikimedia/phabricator-arcanist,folsom-labs/arcanist,codelabs-ch/arcanist,alexmv/arcanist,phacility/arcanist,wxstars/arcanist,chundongwang/arcanist,alexmv/arcanist,phacility/arcanist,phacility/arcanist,codelabs-ch/arcanist,chundongwang/arcanist,calblueprint/arcanist,kevinseelbach/arcanist,KieranHayes/arcanist,zhihu/arcanist,zhihu/arcanist,Symplicity/arcanist,fivestars/arcanist,eSpark/arcanist,calblueprint/arcanist,folsom-labs/arcanist,PageUpPeopleOrg/arcanist-patches,aik099/arcanist,uber/arcanist,codelabs-ch/arcanist,memsql/arcanist,Khan/arcanist,Symplicity/arcanist,eSpark/arcanist,PageUpPeopleOrg/arcanist-patches,aik099/arcanist,eSpark/arcanist,haskell-infra/arcanist,folsom-labs/arcanist,kevinseelbach/arcanist,wikimedia/phabricator-arcanist,uber/arcanist,r4nt/arcanist,wikimedia/phabricator-arcanist,zhihu/arcanist,coursera/arcanist,KieranHayes/arcanist,wxstars/arcanist,KieranHayes/arcanist,wharris/arcanist,hach-que/arcanist,fivestars/arcanist,calblueprint/arcanist,wharris/arcanist,calblueprint/arcanist,fivestars/arcanist,chundongwang/arcanist,coursera/arcanist,wxstars/arcanist,folsom-labs/arcanist,haskell-infra/arcanist,jra3/arcanist,hach-que/arcanist,uber/arcanist,codelabs-ch/arcanist,alexmv/arcanist