win_defs.h: redefine RGB macro after undefining

Before this change, if os_defs.h was included after macros.h then
win_defs.h would undefine our own RGB macro.

vim-patch:8.0.0146

src/nvim/os/win_defs.h

@@ -30,8 +30,13 @@
 
 #define USE_CRNL
 
-// We have our own RGB macro in macros.h.
-#undef RGB
+// Windows defines a RGB macro that produces 0x00bbggrr color values for use
+// with GDI. Our macro is different, and we don't use GDI.
+#if defined(RGB)
+# undef RGB
+  // Duplicated from macros.h to avoid include-order sensitivity.
+# define RGB(r, g, b) ((r << 16) | (g << 8) | b)
+#endif
 
 #ifdef _MSC_VER
 # ifndef inline

src/nvim/version.c

@@ -806,7 +806,7 @@ static const int included_patches[] = {
   // 149,
   // 148,
   // 147,
-  // 146,
+  146,
   // 145 NA
   // 144 NA
   // 143,