[gtk/gtk-3-24] build/win32/detectenv-msvc.mak: Update error message

[Chun-wei Fan <fanchunwei src gnome org>]

commit 2d3c0e9e7d74a9decf7b933e8eabdb01bffe41c5
Author: Chun-wei Fan <fanchunwei src gnome org>
Date:   Tue Jun 18 16:30:58 2019 +0800

    build/win32/detectenv-msvc.mak: Update error message
    
    We now support up to Visual Studio 2019, not just 2015, so don't
    confuse people here...

 build/win32/detectenv-msvc.mak | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/build/win32/detectenv-msvc.mak b/build/win32/detectenv-msvc.mak
index acecbf5885..787a897417 100644
--- a/build/win32/detectenv-msvc.mak
+++ b/build/win32/detectenv-msvc.mak
@@ -53,7 +53,7 @@ VSVER = 0
 !if "$(VSVER)" == "0"
 MSG = ^
 This NMake Makefile set supports Visual Studio^
-9 (2008) through 14 (2015).  Your Visual Studio^
+9 (2008) through 16 (2019).  Your Visual Studio^
 version is not supported.
 !error $(MSG)
 !endif