Spyc is not required in Framework.php

Summary: Accidentally added in D1263642

Reviewed By: @ptarjan

Differential Revision: D1274047
Move m_savedRbp spill from FPushFunc*/SpillFrame to FCall/Call

Summary: Make m_savedRbp spill consistent with m_savedRip/m_soff spills and do it
at FCall time rather than FPushFunc* time.

Reviewed By: @jdelong

Differential Revision: D1281465
Make arGetSfp() more sane and rename it to sfp()

Summary: - no good reason to return the same fp if there is no saved fp; return nullptr instead
- rename ActRec::arGetSfp() to ActRec::sfp()
- rename ActRec::m_savedRbp to ActRec::m_sfp and change its type to ActRec*
- kill arSetSfp()
- simplify related code
- make sfp() return nullptr when in resumed async function; m_sfp is currently always nullptr in this case, but this adds ability to reuse this field to return from async functions directly into the caller async function (one of its parents)

Reviewed By: @markw65

Differential Revision: D1281656
Kill async stack overflow checks

Summary: Async stack overflow checks were used to detect unbounded async
recursion. It's too troublesome to maintain this feature and it
currently blocks an attempt to remove active tracking of currently
running async function.

The side effect of this change is that instead of injecting exception at
random place early (possibly in a context that did not expect any
exceptions), we let the request run until it runs out of memory.

Reviewed By: @billf

Differential Revision: D1285431
Update third-party to fix MacOSX