testing package does not support Benchmarks

[13rac1]

The following test file:

package main

import (
	"testing"
)

func BenchmarkTest(b *testing.B) {
}

Fails with:

$ tinygo test
# github.com/user/test
main_test.go:7:31: B not declared by package testing

Would be nice if the test file would compile, but ignore Benchmarks. Probably a good starter PR for myself. Done.

Definitely a low priority issue for now

[deadprogram]

This has been released with 0.8.0 so now closing. Thank you.