Updated Upstream (Bukkit/CraftBukkit/Spigot)

Upstream has released updates that appears to apply and compile correctly.
This update has not been tested by PaperMC and as with ANY update, please do your own testing

Please note that this build includes changes to meet upstreams
requirements for nullability annotations. While we aim for a level of
accuracy, these might not be 100% correct, if there are any issues,
please speak to us on discord, or open an issue on the tracker to
discuss.

Bukkit Changes:
9a6a1de3 Remove nullability annotations from enum constructors
3f0591ea SPIGOT-2540: Add nullability annotations to entire Bukkit API

CraftBukkit Changes:
8d8475fc SPIGOT-4666: Force parameter in HumanEntity#sleep
8b1588e2 Fix ExplosionPrimeEvent#setFire not working with EnderCrystals
39a287b7 Don't ignore newlines in PlayerListHeader/Footer

Spigot Changes:
cf694d87 Add nullability annotations

Spigot-API-Patches/0001-POM-changes.patch

@@ -1,11 +1,11 @@
-From 02d5007d081bde67f58dac3e04ce1df9e70ff9b4 Mon Sep 17 00:00:00 2001
+From 16f2fa8f86ea4272386830faf08c84cde635a753 Mon Sep 17 00:00:00 2001
 From: Zach Brown <zach.brown@destroystokyo.com>
 Date: Tue, 1 Mar 2016 00:16:08 +0100
 Subject: [PATCH] POM changes
 
 
 diff --git a/pom.xml b/pom.xml
-index 23fde9622..a613cf963 100644
+index b3369ecf..c2ec40c7 100644
 --- a/pom.xml
 +++ b/pom.xml
 @@ -3,33 +3,28 @@
@@ -80,7 +80,7 @@ index 23fde9622..a613cf963 100644
          <!-- bundled with Minecraft, should be kept in sync -->
          <dependency>
              <groupId>com.google.guava</groupId>
-@@ -107,15 +113,12 @@
+@@ -119,15 +125,12 @@
      </dependencies>
  
      <build>
@@ -97,7 +97,7 @@ index 23fde9622..a613cf963 100644
                  <dependencies>
                      <!-- we need our custom version as it fixes some bugs on case sensitive file systems -->
                      <dependency>
-@@ -150,6 +153,7 @@
+@@ -162,6 +165,7 @@
                      </execution>
                  </executions>
                  <configuration>
@@ -106,5 +106,5 @@ index 23fde9622..a613cf963 100644
                      <shadedArtifactAttached>true</shadedArtifactAttached>
                  </configuration>
 -- 
-2.20.1
+2.21.0