Remove catastrophic from MD_Error and add MD_MessageKind to it.

source/md.h

@@ -380,8 +380,9 @@ struct MD_CodeLoc
 
 typedef enum MD_MessageKind
 {
-    MD_MessageKind_Error,
+    MD_MessageKind_None,
     MD_MessageKind_Warning,
+    MD_MessageKind_Error,
 }
 MD_MessageKind;
 
@@ -487,7 +488,7 @@ struct MD_Error
     MD_String8 string;
     MD_String8 filename;
     MD_Node *node;
-    MD_b32 catastrophic;
+    MD_MessageKind kind;
 };
 
 typedef struct MD_ParseCtx MD_ParseCtx;
@@ -502,6 +503,7 @@ struct MD_ParseCtx
     MD_String8 file_contents;
     MD_Map namespace_table;
     MD_Node *selected_namespace;
+    MD_MessageKind error_level;
     MD_b32 catastrophic_error;
 };