Added missing #include.

Fix warnings on MSVC: the code should now be clean with -W4.
Fix warnings on gcc: the code should now be clean with -Wall -Wshadow.
This fixes Track issues #585, #980, #1196, #1278 and #1340.

[SVN r41254]

libs/format

@@ -1 +1 @@
-Subproject commit 2b907bc09e432256000fa4ef196c8ae7c9cffa9e
+Subproject commit 840ee87985c2417b02f3392a0487aa2031579c35