Fix -Wthread-safety-analysis warnings. Compile with -Wthread-safety-analysis if available.

Summary:

• Use -Wthread-safety-analysis if available (+ -Werror=thread-safety-analysis if --enable-werror)

• Fix -Wthread-safety-analysis warnings. Change the sync.h primitives to std from boost.

Commit 1.

This code was written by @TheBlueMatt in the following branch:

• https://github.com/TheBlueMatt/bitcoin/commits/2017-08-test-10923

This commit message was written by me (@practicalswift) who also squashed
@TheBlueMatt's commits into one and tried to summarize the changes made.

Commit 2.

Remove boost include. Remove boost mentions in comments.

• Add mutex requirement for AddToCompactExtraTransactions(…)

The vector vExtraTxnForCompact, which is guarded by the mutex
cs_main, is accessed in AddToCompactExtraTransactions(…).

This is a backport of Core PR10866

Test Plan:

make check

Reviewers: #bitcoin_abc, jasonbcox

Reviewed By: #bitcoin_abc, jasonbcox

Subscribers: teamcity

Differential Revision: https://reviews.bitcoinabc.org/D1902