Recursive call crashes gpython

We define a function and recursive call the function in test.py crashing gpython. This case cannot crash CPython and it reports a RecursionError.

test.py:
```
def f():
f()
f()
```

Expected output: RecursionError

Actual output:
runtime: goroutine stack exceeds 1000000000-byte limit
fatal error: stack overflow

runtime stack:
runtime.throw(0x66c609, 0xe)
/opt/go/go1.11/src/runtime/panic.go:608 +0x72
runtime.newstack()
/opt/go/go1.11/src/runtime/stack.go:1008 +0x729
runtime.morestack()
/opt/go/go1.11/src/runtime/asm_amd64.s:429 +0x8f
goroutine 1 [running]:
runtime.heapBitsSetType(0xc0027a3440, 0x30, 0x30, 0x658180)
/opt/go/go1.11/src/runtime/mbitmap.go:911 +0xa30 fp=0xc0226e2390 sp=0xc0226e2388 pc=0x416c80
runtime.mallocgc(0x30, 0x658180, 0x1, 0x0)
/home/ncw/go/src/github.com/go-python/gpython/vm/eval.go:1428 +0x40 fp=0xc0226e83c8 sp=0xc0226e8378 pc=0x5b33d0
...additional frames elided...
.......................
goroutine 19 [syscall]:
os/signal.signal_recv(0x0)
/opt/go/go1.11/src/runtime/sigqueue.go:139 +0x9c
os/signal.loop()
/opt/go/go1.11/src/os/signal/signal_unix.go:23 +0x22
created by os/signal.init.0
/opt/go/go1.11/src/os/signal/signal_unix.go:29 +0x41

version: Gpython3.4.0 on Ubuntu 16.04