Refactor AST and Parser into modular subdirectories

- Split ast.h into granular headers in v0/ast/
- Split parser.c into modular implementation files in v0/parser/
- Move and rename parser tests to v0/parser/test_*.c
- Update build system (include.mk) with modular sub-makefiles
- Maintain v0/ast.h and v0/parser.h as umbrella headers

v0/test.c

@@ -189,7 +189,10 @@ typedef struct {
 } TestCase;
 
 #include "test_token.c"
-#include "test_parser.c"
+#include "parser/test_module.c"
+#include "parser/test_declaration.c"
+#include "parser/test_expression.c"
+#include "parser/test_core.c"
 #include "test_log.c"
 
 static int s_totalTests;
@@ -201,20 +204,23 @@ static TestCase s_tests[] = {
     TEST(test_log_error)
     TEST(test_log_on_line_variadic)
     TEST(test_log_on_line)
-    TEST(test_parser_alias_array)
-    TEST(test_parser_alias_simple)
-    TEST(test_parser_bad_import_name)
-    TEST(test_parser_bad_module_name)
-    TEST(test_parser_imports)
-    TEST(test_parser_missing_semicolon_import)
-    TEST(test_parser_missing_semicolon_module)
     TEST(test_parser_module_name)
+    TEST(test_parser_bad_module_name)
+    TEST(test_parser_missing_semicolon_module)
+    TEST(test_parser_missing_semicolon_import)
+    TEST(test_parser_bad_import_name)
+    TEST(test_parser_imports)
     TEST(test_parser_public_imports)
+    TEST(test_parser_alias_simple)
+    TEST(test_parser_alias_simple_type)
+    TEST(test_parser_alias_array)
     TEST(test_parser_variable_simple)
+    TEST(test_parser_variable_simple_type)
     TEST(test_parser_variable_const)
     TEST(test_parser_variable_init)
     TEST(test_parser_variable_static)
     TEST(test_parser_multiple_vars)
+    TEST(test_parser_core_placeholder)
     TEST(test_tokenstream_comma)
     TEST(test_tokenstream_info)
     TEST(test_tokenstream_keywords_and_symbols)