Fix playground (#325)

Author: vtereshkov

playground/umka.js

@@ -351,10 +351,10 @@ fn error*(code: int = 0, msg: str = "", sender: any = null): Err {
 
 fn exitif*(err: Err) {
     if err.code != 0 {
-        fprintf(stderr(), "Runtime error: %s (code %d) in %v\n", err.msg, err.code, err.sender)
-        fprintf(stderr(), "Stack trace:\n")
+        printf("Runtime error: %s (code %d) in %v\n", err.msg, err.code, err.sender)
+        printf("Stack trace:\n")
         for _, pos in err.trace {
-            fprintf(stderr(), "    %s: %s (%d)\n", pos.func, pos.file, pos.line)
+            printf("    %s: %s (%d)\n", pos.func, pos.file, pos.line)
         }
         exit(err.code)
     }    

runtime/std.um

@@ -362,10 +362,10 @@ static const char *runtimeModuleSources[] = {
 "\n"
 "fn exitif*(err: Err) {\n"
 "    if err.code != 0 {\n"
-"        fprintf(stderr(), \"Runtime error: %s (code %d) in %v\\n\", err.msg, err.code, err.sender)\n"
-"        fprintf(stderr(), \"Stack trace:\\n\")\n"
+"        printf(\"Runtime error: %s (code %d) in %v\\n\", err.msg, err.code, err.sender)\n"
+"        printf(\"Stack trace:\\n\")\n"
 "        for _, pos in err.trace {\n"
-"            fprintf(stderr(), \"    %s: %s (%d)\\n\", pos.func, pos.file, pos.line)\n"
+"            printf(\"    %s: %s (%d)\\n\", pos.func, pos.file, pos.line)\n"
 "        }\n"
 "        exit(err.code)\n"
 "    }    \n"