Build placeholder token names with a fixed locale

Placeholder names were built with bare toLowerCase(), which follows
the JVM default locale; on Turkish-locale JVMs enum names containing
'I' produce a dotless ı, so tokens like mctop_mining would register
under a different spelling than documented. The case-insensitive token
map happens to absorb the mismatch, but the registered names should
not depend on that. All seven placeholder classes now lower-case with
Locale.ENGLISH.

src/main/java/com/gmail/nossr50/placeholders/McTopPlaceholder.java

@@ -1,6 +1,7 @@
 package com.gmail.nossr50.placeholders;
 
 import com.gmail.nossr50.datatypes.skills.PrimarySkillType;
+import java.util.Locale;
 import java.util.function.IntFunction;
 import org.bukkit.entity.Player;
 import org.jetbrains.annotations.Nullable;
@@ -75,7 +76,7 @@ public class McTopPlaceholder implements Placeholder {
     }
 
     private static String token(@Nullable PrimarySkillType skill, String overallToken) {
-        return skill == null ? overallToken : skill.toString().toLowerCase();
+        return skill == null ? overallToken : skill.toString().toLowerCase(Locale.ENGLISH);
     }
 
     @Override

src/main/java/com/gmail/nossr50/placeholders/SkillExpNeededPlaceholder.java

@@ -1,6 +1,7 @@
 package com.gmail.nossr50.placeholders;
 
 import com.gmail.nossr50.datatypes.skills.PrimarySkillType;
+import java.util.Locale;
 import org.bukkit.entity.Player;
 
 public class SkillExpNeededPlaceholder implements Placeholder {
@@ -21,6 +22,6 @@ public class SkillExpNeededPlaceholder implements Placeholder {
 
     @Override
     public String getName() {
-        return "xp_needed_" + skillType.toString().toLowerCase();
+        return "xp_needed_" + skillType.toString().toLowerCase(Locale.ENGLISH);
     }
 }

src/main/java/com/gmail/nossr50/placeholders/SkillExpPlaceholder.java

@@ -1,6 +1,7 @@
 package com.gmail.nossr50.placeholders;
 
 import com.gmail.nossr50.datatypes.skills.PrimarySkillType;
+import java.util.Locale;
 import org.bukkit.entity.Player;
 
 public class SkillExpPlaceholder implements Placeholder {
@@ -21,6 +22,6 @@ public class SkillExpPlaceholder implements Placeholder {
 
     @Override
     public String getName() {
-        return "xp_" + skill.toString().toLowerCase();
+        return "xp_" + skill.toString().toLowerCase(Locale.ENGLISH);
     }
 }

src/main/java/com/gmail/nossr50/placeholders/SkillExpRemainingPlaceholder.java

@@ -1,6 +1,7 @@
 package com.gmail.nossr50.placeholders;
 
 import com.gmail.nossr50.datatypes.skills.PrimarySkillType;
+import java.util.Locale;
 import org.bukkit.entity.Player;
 
 public class SkillExpRemainingPlaceholder implements Placeholder {
@@ -20,6 +21,6 @@ public class SkillExpRemainingPlaceholder implements Placeholder {
 
     @Override
     public String getName() {
-        return "xp_remaining_" + skill.toString().toLowerCase();
+        return "xp_remaining_" + skill.toString().toLowerCase(Locale.ENGLISH);
     }
 }

src/main/java/com/gmail/nossr50/placeholders/SkillLevelPlaceholder.java

@@ -1,6 +1,7 @@
 package com.gmail.nossr50.placeholders;
 
 import com.gmail.nossr50.datatypes.skills.PrimarySkillType;
+import java.util.Locale;
 import org.bukkit.entity.Player;
 
 public class SkillLevelPlaceholder implements Placeholder {
@@ -20,6 +21,6 @@ public class SkillLevelPlaceholder implements Placeholder {
 
     @Override
     public String getName() {
-        return "level_" + skillType.toString().toLowerCase();
+        return "level_" + skillType.toString().toLowerCase(Locale.ENGLISH);
     }
 }

src/main/java/com/gmail/nossr50/placeholders/SkillRankPlaceholder.java

@@ -1,6 +1,7 @@
 package com.gmail.nossr50.placeholders;
 
 import com.gmail.nossr50.datatypes.skills.PrimarySkillType;
+import java.util.Locale;
 import org.bukkit.entity.Player;
 
 public class SkillRankPlaceholder implements Placeholder {
@@ -20,6 +21,6 @@ public class SkillRankPlaceholder implements Placeholder {
 
     @Override
     public String getName() {
-        return "rank_" + skill.toString().toLowerCase();
+        return "rank_" + skill.toString().toLowerCase(Locale.ENGLISH);
     }
 }

src/main/java/com/gmail/nossr50/placeholders/SkillXpRatePlaceholder.java

@@ -1,6 +1,7 @@
 package com.gmail.nossr50.placeholders;
 
 import com.gmail.nossr50.datatypes.skills.PrimarySkillType;
+import java.util.Locale;
 import org.bukkit.entity.Player;
 
 public class SkillXpRatePlaceholder implements Placeholder {
@@ -20,6 +21,6 @@ public class SkillXpRatePlaceholder implements Placeholder {
 
     @Override
     public String getName() {
-        return "xprate_" + skillType.toString().toLowerCase();
+        return "xprate_" + skillType.toString().toLowerCase(Locale.ENGLISH);
     }
 }