[geary] Fix compilation error with valac < 0.38.1-ish.

[Michael Gratton <mjog src gnome org>]

commit 9e2a2f03b4e28b3dd2025cb8e05ccf7faff3910c
Author: Michael James Gratton <mike vee net>
Date:   Fri Apr 13 23:06:58 2018 +1000

    Fix compilation error with valac < 0.38.1-ish.
    
    * src/engine/imap/command/imap-create-command.vala (Command): Rename
      atom consts so they do not collide with GObject property names defines
      generated by older version of valac.

 src/engine/imap/command/imap-create-command.vala |    8 ++++----
 1 files changed, 4 insertions(+), 4 deletions(-)
---
diff --git a/src/engine/imap/command/imap-create-command.vala 
b/src/engine/imap/command/imap-create-command.vala
index e235faa..0401a26 100644
--- a/src/engine/imap/command/imap-create-command.vala
+++ b/src/engine/imap/command/imap-create-command.vala
@@ -17,8 +17,8 @@
  */
 public class Geary.Imap.CreateCommand : Command {
 
-    public const string NAME = "create";
-    public const string USE = "use";
+    public const string NAME_ATOM = "create";
+    public const string USE_ATOM = "use";
 
     public MailboxSpecifier mailbox { get; private set; }
 
@@ -56,7 +56,7 @@ public class Geary.Imap.CreateCommand : Command {
     }
 
     public CreateCommand(MailboxSpecifier mailbox) {
-        base(NAME);
+        base(NAME_ATOM);
         this.mailbox = mailbox;
         add(mailbox.to_parameter());
     }
@@ -72,7 +72,7 @@ public class Geary.Imap.CreateCommand : Command {
             use_types.add(new AtomParameter(attr.to_string()));
 
             ListParameter use_param = new ListParameter();
-            use_param.add(new AtomParameter(USE));
+            use_param.add(new AtomParameter(USE_ATOM));
             use_param.add(use_types);
 
             add(use_param);