Merge branch 'release-6.6.4'
Merge branch 'develop'
Merge branch 'develop'
[[ Valgrind ]] Add valgrind headers to headers/linux/include.

Ensures that Linux _DEBUG builds can always be created with support
for Valgrind debugging of MCValue buffer pools.
Merge pull request #14 from peter-b/misc-valgrindpools

[[ Valgrind ]] Include Valgrind / Memcheck headers in thirdparty.