[gimp] devel-docs: update macOS support to OSX 10.12 on master.

[Jehan <jehanp src gnome org>]

commit a89c4738cc0ec7500374d8c02ae9aa41b2d08104
Author: Jehan <jehan girinstud io>
Date:   Wed Jun 27 16:08:50 2018 +0200

    devel-docs: update macOS support to OSX 10.12 on master.
    
    We diverge from the gimp-2-10 branch by setting a higher minimum
    support for the GTK+3 port, as discussed with Mitch and Samm.

 devel-docs/os-support.txt | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)
---
diff --git a/devel-docs/os-support.txt b/devel-docs/os-support.txt
index 81057477f8..93acf3ba83 100644
--- a/devel-docs/os-support.txt
+++ b/devel-docs/os-support.txt
@@ -13,8 +13,10 @@ Minimum dependency versions can be bumped if available in Debian Testing.
 
 ### macOS
 
-Compatibility with 10.9 and over.
+Compatibility with 10.12 and over.
+64-bit only.
 
 ### Windows
 
 Windows 7 and over.
+32 and 64-bit.