New utility function logevent_and_free.

This should make it easier to do formatted-string based logging
outside ssh.c, because I can wrap up a local macro in any source file
I like that expands to logevent_and_free(wherever my Frontend is,
dupprintf(macro argument)).

It caused yet another stub function to be needed in testbn, but there
we go.

(Also, while I'm here, removed a redundant declaration of logevent
itself from ssh.h. The one in putty.h is all we need.)

misc.c

@@ -337,6 +337,12 @@ void burnstr(char *string)             /* sfree(str), only clear it first */
     }
 }
 
+void logevent_and_free(Frontend *frontend, char *s)
+{
+    logevent(frontend, s);
+    sfree(s);
+}
+
 int toint(unsigned u)
 {
     /*

misc.h

@@ -31,6 +31,13 @@ char *dupprintf(const char *fmt, ...)
 char *dupvprintf(const char *fmt, va_list ap);
 void burnstr(char *string);
 
+/*
+ * Pass a dynamically allocated string to logevent and immediately
+ * free it. Intended for use by wrapper macros which pass the return
+ * value of dupprintf straight to this.
+ */
+void logevent_and_free(Frontend *frontend, char *msg);
+
 struct strbuf {
     char *s;
     unsigned char *u;

ssh.h

@@ -777,8 +777,6 @@ int random_byte(void);
 void random_add_noise(void *noise, int length);
 void random_add_heavynoise(void *noise, int length);
 
-void logevent(Frontend *, const char *);
-
 /* Exports from x11fwd.c */
 enum {
     X11_TRANS_IPV4 = 0, X11_TRANS_IPV6 = 6, X11_TRANS_UNIX = 256

testbn.c

@@ -7,6 +7,7 @@
  * testdata/bignum.py.
  */
 
+#include <assert.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <ctype.h>
@@ -31,6 +32,8 @@ int random_byte(void)
     return 0;
 }
 
+void logevent(Frontend *frontend, const char *msg) { assert(0); }
+
 #define fromxdigit(c) ( (c)>'9' ? ((c)&0xDF) - 'A' + 10 : (c) - '0' )
 
 /* For Unix in particular, but harmless if this main() is reused elsewhere */

windows/winpgen.c

@@ -60,6 +60,9 @@ void nonfatal(const char *fmt, ...)
     sfree(stuff);
 }
 
+/* Stub needed to link against misc.c */
+void logevent(Frontend *frontend, const char *msg) { assert(0); }
+
 /* ----------------------------------------------------------------------
  * Progress report code. This is really horrible :-)
  */

windows/winpgnt.c

@@ -113,6 +113,9 @@ static void unmungestr(char *in, char *out, int outlen)
     return;
 }
 
+/* Stub needed to link against misc.c */
+void logevent(Frontend *frontend, const char *msg) { assert(0); }
+
 static int has_security;
 
 struct PassphraseProcStruct {