patch 8.0.1785: missing symbol in Win32 small build

Problem:    Missing symbol in Win32 small build.
Solution:   Define VTERM_ANSI_INDEX_NONE without the terminal feature. Also
            fix unused function with #ifdef.

src/os_win32.c

@@ -7656,6 +7656,7 @@ vtp_sgr_bulks(
     vtp_printf((char *)buf);
 }
 
+# ifdef FEAT_TERMGUICOLORS
     static int
 ctermtoxterm(
     int cterm)
@@ -7665,6 +7666,7 @@ ctermtoxterm(
     cterm_color2rgb(cterm, &r, &g, &b, &idx);
     return (((int)r << 16) | ((int)g << 8) | (int)b);
 }
+# endif
 
     static void
 set_console_color_rgb(void)

src/term.c

@@ -6977,6 +6977,8 @@ static int grey_ramp[] = {
 
 # ifdef FEAT_TERMINAL
 #  include "libvterm/include/vterm.h"  // for VTERM_ANSI_INDEX_NONE
+# else
+#  define VTERM_ANSI_INDEX_NONE 0
 # endif
 
 static uint8_t ansi_table[16][4] = {

src/version.c

@@ -761,6 +761,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1785,
 /**/
     1784,
 /**/