refactor: move non-symbols in mbyte.h to mbyte_defs.h

This just avoids including mbyte.h in eval/typval.h, so that mbyte.h can
include eval/typval.h in Vim patch 8.2.1535.

src/nvim/mbyte.h

@@ -6,7 +6,7 @@
 #include <string.h>
 
 #include "nvim/func_attr.h"
-#include "nvim/iconv.h"
+#include "nvim/mbyte_defs.h"
 #include "nvim/os/os_defs.h"  // For indirect
 #include "nvim/types.h"  // for char_u
 
@@ -19,52 +19,6 @@
 #define MB_BYTE2LEN(b)         utf8len_tab[b]
 #define MB_BYTE2LEN_CHECK(b)   (((b) < 0 || (b) > 255) ? 1 : utf8len_tab[b])
 
-// max length of an unicode char
-#define MB_MAXCHAR     6
-
-// properties used in enc_canon_table[] (first three mutually exclusive)
-#define ENC_8BIT       0x01
-#define ENC_DBCS       0x02
-#define ENC_UNICODE    0x04
-
-#define ENC_ENDIAN_B   0x10        // Unicode: Big endian
-#define ENC_ENDIAN_L   0x20        // Unicode: Little endian
-
-#define ENC_2BYTE      0x40        // Unicode: UCS-2
-#define ENC_4BYTE      0x80        // Unicode: UCS-4
-#define ENC_2WORD      0x100       // Unicode: UTF-16
-
-#define ENC_LATIN1     0x200       // Latin1
-#define ENC_LATIN9     0x400       // Latin9
-#define ENC_MACROMAN   0x800       // Mac Roman (not Macro Man! :-)
-
-/// Flags for vimconv_T
-typedef enum {
-  CONV_NONE      = 0,
-  CONV_TO_UTF8   = 1,
-  CONV_9_TO_UTF8 = 2,
-  CONV_TO_LATIN1 = 3,
-  CONV_TO_LATIN9 = 4,
-  CONV_ICONV     = 5,
-} ConvFlags;
-
-#define MBYTE_NONE_CONV { \
-  .vc_type = CONV_NONE, \
-  .vc_factor = 1, \
-  .vc_fail = false, \
-}
-
-/// Structure used for string conversions
-typedef struct {
-  int vc_type;  ///< Zero or more ConvFlags.
-  int vc_factor;  ///< Maximal expansion factor.
-#ifdef HAVE_ICONV
-  iconv_t vc_fd;  ///< Value for CONV_ICONV.
-#endif
-  bool vc_fail;  ///< What to do with invalid characters: if true, fail,
-                 ///< otherwise use '?'.
-} vimconv_T;
-
 extern const uint8_t utf8len_tab_zero[256];
 
 extern const uint8_t utf8len_tab[256];