patch 8.1.0338: MS-Windows: VTP doesn't work properly with Powershell

Problem:    MS-Windows: VTP doesn't work properly with Powershell.
Solution:   Adjust the color index. (Nobuhiro Takasaki, closes #3347)
diff --git a/src/os_win32.c b/src/os_win32.c
index 2cfcecf..02bcaae 100644
--- a/src/os_win32.c
+++ b/src/os_win32.c
@@ -213,6 +213,14 @@
 static guicolor_T save_console_bg_rgb;
 static guicolor_T save_console_fg_rgb;
 
+static int g_color_index_bg = 0;
+static int g_color_index_fg = 7;
+
+# ifdef FEAT_TERMGUICOLORS
+static int default_console_color_bg = 0x000000; // black
+static int default_console_color_fg = 0xc0c0c0; // white
+# endif
+
 # ifdef FEAT_TERMGUICOLORS
 #  define USE_VTP		(vtp_working && is_term_win32() && (p_tgc || (!p_tgc && t_colors >= 256)))
 # else
@@ -2628,6 +2636,10 @@
     if (cterm_normal_bg_color == 0)
 	cterm_normal_bg_color = ((g_attrCurrent >> 4) & 0xf) + 1;
 
+    // Fg and Bg color index nunmber at startup
+    g_color_index_fg = g_attrDefault & 0xf;
+    g_color_index_bg = (g_attrDefault >> 4) & 0xf;
+
     /* set termcap codes to current text attributes */
     update_tcap(g_attrCurrent);
 
@@ -7664,6 +7676,9 @@
     DWORD   ver, mode;
     HMODULE hKerneldll;
     DYN_CONSOLE_SCREEN_BUFFER_INFOEX csbi;
+# ifdef FEAT_TERMGUICOLORS
+    COLORREF fg, bg;
+# endif
 
     ver = get_build_number();
     vtp_working = (ver >= VTP_FIRST_SUPPORT_BUILD) ? 1 : 0;
@@ -7690,8 +7705,17 @@
     csbi.cbSize = sizeof(csbi);
     if (has_csbiex)
 	pGetConsoleScreenBufferInfoEx(g_hConOut, &csbi);
-    save_console_bg_rgb = (guicolor_T)csbi.ColorTable[0];
-    save_console_fg_rgb = (guicolor_T)csbi.ColorTable[7];
+    save_console_bg_rgb = (guicolor_T)csbi.ColorTable[g_color_index_bg];
+    save_console_fg_rgb = (guicolor_T)csbi.ColorTable[g_color_index_fg];
+
+# ifdef FEAT_TERMGUICOLORS
+    bg = (COLORREF)csbi.ColorTable[g_color_index_bg];
+    fg = (COLORREF)csbi.ColorTable[g_color_index_fg];
+    bg = (GetRValue(bg) << 16) | (GetGValue(bg) << 8) | GetBValue(bg);
+    fg = (GetRValue(fg) << 16) | (GetGValue(fg) << 8) | GetBValue(fg);
+    default_console_color_bg = bg;
+    default_console_color_fg = fg;
+#endif
 
     set_console_color_rgb();
 }
@@ -7788,14 +7812,16 @@
 	ctermfg = -1;
 	if (id > 0)
 	    syn_id2cterm_bg(id, &ctermfg, &ctermbg);
-	fg = ctermfg != -1 ? ctermtoxterm(ctermfg) : 0xc0c0c0; /* white */
+	fg = ctermfg != -1 ? ctermtoxterm(ctermfg) : default_console_color_fg;
+	cterm_normal_fg_gui_color = fg;
     }
     if (bg == INVALCOLOR)
     {
 	ctermbg = -1;
 	if (id > 0)
 	    syn_id2cterm_bg(id, &ctermfg, &ctermbg);
-	bg = ctermbg != -1 ? ctermtoxterm(ctermbg) : 0x000000; /* black */
+	bg = ctermbg != -1 ? ctermtoxterm(ctermbg) : default_console_color_bg;
+	cterm_normal_bg_gui_color = bg;
     }
     fg = (GetRValue(fg) << 16) | (GetGValue(fg) << 8) | GetBValue(fg);
     bg = (GetRValue(bg) << 16) | (GetGValue(bg) << 8) | GetBValue(bg);
@@ -7807,8 +7833,8 @@
     csbi.cbSize = sizeof(csbi);
     csbi.srWindow.Right += 1;
     csbi.srWindow.Bottom += 1;
-    csbi.ColorTable[0] = (COLORREF)bg;
-    csbi.ColorTable[7] = (COLORREF)fg;
+    csbi.ColorTable[g_color_index_bg] = (COLORREF)bg;
+    csbi.ColorTable[g_color_index_fg] = (COLORREF)fg;
     if (has_csbiex)
 	pSetConsoleScreenBufferInfoEx(g_hConOut, &csbi);
 # endif
@@ -7827,8 +7853,8 @@
     csbi.cbSize = sizeof(csbi);
     csbi.srWindow.Right += 1;
     csbi.srWindow.Bottom += 1;
-    csbi.ColorTable[0] = (COLORREF)save_console_bg_rgb;
-    csbi.ColorTable[7] = (COLORREF)save_console_fg_rgb;
+    csbi.ColorTable[g_color_index_bg] = (COLORREF)save_console_bg_rgb;
+    csbi.ColorTable[g_color_index_fg] = (COLORREF)save_console_fg_rgb;
     if (has_csbiex)
 	pSetConsoleScreenBufferInfoEx(g_hConOut, &csbi);
 # endif