ident.h: move ident-related declarations out of cache.h

These functions were all defined in a separate ident.c already, so
create ident.h and move the declarations into that file.

Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

gpg-interface.c

@@ -4,6 +4,7 @@
 #include "run-command.h"
 #include "strbuf.h"
 #include "dir.h"
+#include "ident.h"
 #include "gpg-interface.h"
 #include "sigchain.h"
 #include "tempfile.h"