Fix numerous VC-10 compiler warnings.

Rewrite ICU configuration to use the new Boost.Build configuration logic.

[SVN r61893]

example/snippets/partial_regex_grep.cpp

@@ -61,7 +61,7 @@ void search(std::istream& is)
       std::memmove(buf, next_pos, leftover);
       // fill the rest from the stream:
       is.read(buf + leftover, size);
-      unsigned read = is.gcount();
+      std::streamsize read = is.gcount();
       // check to see if we've run out of text:
       have_more = read == size;
       // reset next_pos: