Fixed a typo in code for setting the default tag joiner character in the Boost Build tools/common.jam module. Caught and reported by Steven Watanabe.

[SVN r47370]

tools/build

@@ -1 +1 @@
-Subproject commit 9838fecf0469a05500fd4b509e13b0c0ab89f886
+Subproject commit bd213a62da9740d5bd1b1ea5e3297a2b89d8e817