imap-send: include strbuf.h

We make liberal use of the strbuf API functions and types, but the
inclusion of <strbuf.h> comes indirectly by including <http.h>,
which does not happen if you build with NO_CURL.

Signed-off-by: Christian Hesse <mail@eworm.de>
Helped-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

imap-send.c

@@ -29,6 +29,7 @@
 #include "run-command.h"
 #include "parse-options.h"
 #include "setup.h"
+#include "strbuf.h"
 #include "wrapper.h"
 #if defined(NO_OPENSSL) && !defined(HAVE_OPENSSL_CSPRNG)
 typedef void *SSL;