Issue #3395776 by catch, kristiaanvandeneynde, Wim Leers, Fabianx, larowlan: Make POST requests render cacheable

Issue #3048495 by jonathan1055, quietone, rajandro, Spokje, Pooja Ganjage, andypost, kishor_kolekar, msuthars, munish.kumar, ankithashetty, ayushmishra206, ravi.shankar, naveenvalecha, longwave, Gábor Hojtsy, alexpott, smustgrave, Lendude, xjm, adityasingh, daffie: Fix Drupal.Semantics.FunctionTriggerError coding standard

Issue #2551419 by kristiaanvandeneynde, catch, dawehner, Wim Leers, borisson_, bradjones1, tstoeckler, andypost: Abstract RenderCache into a separate service that is capable of cache redirects in a non-render array-specific way

Issue #2712647 by slasher13, klausi, catch, jibran, Manuel Garcia, alexpott, mpdonadio, naveenvalecha, neclimdul, timmillwood, webflo, dawehner, Wim Leers, pounard: Update Symfony components to ~3.2

Revert "Issue #2712647 by klausi, catch, slasher13, jibran, Manuel Garcia, alexpott, naveenvalecha, neclimdul, dawehner, Wim Leers, pounard: Update Symfony components to ~3.1"

This reverts commit a55b8ef1.

Issue #2712647 by klausi, catch, slasher13, jibran, Manuel Garcia, alexpott, naveenvalecha, neclimdul, dawehner, Wim Leers, pounard: Update Symfony components to ~3.1

Issue #2702609 by Wim Leers, Berdir, Fabianx: Disable placeholdering (and BigPipe) on unsafe requests to help find forms as fast as possible (to allow EnforcedResponses to work)

Issue #2665992 by alexpott, klausi, heykarthikwithu, xjm, tstoeckler: @file is not required for classes, interfaces and traits

Issue #2543334 by Wim Leers, lauriii, Fabianx: Auto-placeholdering for #lazy_builder with bubbling of contexts and tags