reduce arena overrides; tidy up organization of default control macros; eliminate arena casts by directly relying on MD_IMPL_Arena in header

samples/c_code_generation.c

@@ -14,7 +14,7 @@ int main(int argument_count, char **arguments)
     MD_ThreadContext tctx;
     MD_ThreadInit(&tctx);
     
-    arena = MD_ArenaNew(1ull << 40);
+    arena = MD_ArenaAlloc(1ull << 40);
     
     MD_String8 example_code = MD_S8Lit("@struct Foo:\n"
                                        "{\n"

samples/node_errors/node_errors.c

@@ -10,7 +10,7 @@ int main(int argument_count, char **arguments)
     MD_ThreadContext tctx;
     MD_ThreadInit(&tctx);
     
-    arena = MD_ArenaNew(1ull << 40);
+    arena = MD_ArenaAlloc(1ull << 40);
     
     // NOTE(rjf): Parse all the files passed in via command line.
     MD_Node *list = MD_MakeList(arena);

samples/old_style_custom_layer.c

@@ -28,7 +28,7 @@ int main(int argument_count, char **arguments)
     MD_ThreadContext tctx;
     MD_ThreadInit(&tctx);
     
-    arena = MD_ArenaNew(1ull << 40);
+    arena = MD_ArenaAlloc(1ull << 40);
     
     // NOTE(rjf): Parse all the files passed in via command line.
     MD_Node *list = MD_MakeList(arena);

samples/output_parse/output_parse.c

@@ -67,7 +67,7 @@ int main(int argument_count, char **arguments)
     MD_ThreadContext tctx;
     MD_ThreadInit(&tctx);
     
-    arena = MD_ArenaNew(1ull << 40);
+    arena = MD_ArenaAlloc(1ull << 40);
     
     // NOTE(pmh): Parse all the files passed in via command line.
     MD_Node *list = MD_MakeList(arena);

samples/parse_check.c

@@ -8,7 +8,7 @@ int main(int argument_count, char **arguments)
     MD_ThreadContext tctx;
     MD_ThreadInit(&tctx);
     
-    arena = MD_ArenaNew(1ull << 40);
+    arena = MD_ArenaAlloc(1ull << 40);
     
     MD_Node *list = MD_MakeList(arena);
     for(int i = 1; i < argument_count; i += 1)

samples/static_site_generator/static_site_generator.c

@@ -37,7 +37,7 @@ int main(int argument_count, char **arguments)
     MD_ThreadContext tctx;
     MD_ThreadInit(&tctx);
     
-    arena = MD_ArenaNew(1ull << 40);
+    arena = MD_ArenaAlloc(1ull << 40);
     
     //~ NOTE(rjf): Parse command line arguments.
     MD_String8List arg_list = MD_StringListFromArgCV(arena, argument_count, arguments);

samples/toy_language/toy_language.c

@@ -185,7 +185,7 @@ int main(int argument_count, char **arguments)
     MD_ThreadContext tctx;
     MD_ThreadInit(&tctx);
     
-    arena = MD_ArenaNew(1ull << 40);
+    arena = MD_ArenaAlloc(1ull << 40);
     
     //- rjf: parse command line
     MD_String8List arg_list = MD_StringListFromArgCV(arena, argument_count, arguments);