Add ODIN_ERROR_POS_STYLE environment variable

Allowing for two different error message styles:
default or odin
    path(line:column) message
unix
    path:line:column: message

src/error.cpp

@@ -33,6 +33,10 @@ void init_global_error_collector(void) {
 }
 
 
+// temporary
+// defined in build_settings.cpp
+char *token_pos_to_string(TokenPos const &pos);
+
 bool set_file_path_string(i32 index, String const &path) {
 	bool ok = false;
 	GB_ASSERT(index >= 0);