Merge from trunk:

* Silence some buggy VS warnings (fixes #7949)
* Fix -Wconversion warnings (fixes #2558)
* Added support for int128 conversions (fixes #7909)

[SVN r83114]

libs/conversion

@@ -1 +1 @@
-Subproject commit 518203671cfcc8fccb56a504011984c26870da2f
+Subproject commit 335c868e9b276cde41b4a94b61699294d01e2194