New header file 'defs.h'.

This centralises a few things that multiple header files were
previously defining, and were protecting against each other's
redefinition with ifdefs - small things like structs and typedefs. Now
all those things are in a defs.h which is by definition safe to
include _first_ (out of all the codebase-local headers) and only need
to be defined once.

windows/winstuff.h

@@ -23,6 +23,8 @@
 #include <stdint.h>
 #endif
 
+#include "defs.h"
+
 #include "tree234.h"
 
 #include "winhelp.h"
@@ -132,8 +134,6 @@ struct FontSpec *fontspec_new(const char *name,
  *
  * (DECL_WINDOWS_FUNCTION works with both these variants.)
  */
-#define TYPECHECK(to_check, to_return)          \
-    (sizeof(to_check) ? to_return : to_return)
 #define DECL_WINDOWS_FUNCTION(linkage, rettype, name, params)   \
     typedef rettype (WINAPI *t_##name) params;                  \
     linkage t_##name p_##name
@@ -164,13 +164,6 @@ struct FontSpec *fontspec_new(const char *name,
 #endif
 #endif
 
-#ifndef DONE_TYPEDEFS
-#define DONE_TYPEDEFS
-typedef struct conf_tag Conf;
-typedef struct backend_tag Backend;
-typedef struct terminal_tag Terminal;
-#endif
-
 #define PUTTY_REG_POS "Software\\SimonTatham\\PuTTY"
 #define PUTTY_REG_PARENT "Software\\SimonTatham"
 #define PUTTY_REG_PARENT_CHILD "PuTTY"
@@ -198,9 +191,6 @@ typedef struct terminal_tag Terminal;
 
 typedef HDC Context;
 
-typedef unsigned int uint32; /* int is 32-bits on Win32 and Win64. */
-#define PUTTY_UINT32_DEFINED
-
 #ifndef NO_GSSAPI
 /*
  * GSS-API stuff