Various async fixes for release prep v3.15.5#19

Merged

toddouska merged 4 commits intomasterfrom

Nov 9, 2018

Commits on Aug 21, 2018

Fix for conflict for `stat` variable name.
dgarske
committed

Commits on Sep 21, 2018

Fix for possible double free case where ctx->symCtx is not trapped. Improved debug messages.
dgarske
committed

Commits on Nov 2, 2018

Fix for QAT RNG to allow zero length. Resolves PSS test case where `wc_RNG_GenerateBlock` is called for saltLen == 0.
dgarske
committed

Commits on Nov 9, 2018

Rename README.md for easier addition of these sources into wolfssl for release.
dgarske
committed