test/fixedbugs: add more test cases to issue #27718
test/fixedbugs: add more test cases to issue #27718

This CL add test cases for the unary FP negative
operation.

Change-Id: I54e7292ca9df05da0c2b113adefc97ee1e94c6e2
Reviewed-on: https://go-review.googlesource.com/c/go/+/190937
Run-TryBot: Ben Shi <d305faf1f9df9cf68436458fcb54165e72b1642e@163.com>
TryBot-Result: Gobot Gobot <66cb808b70d30c07676d5e946fee83fd561249e5@golang.org>
Reviewed-by: Keith Randall <8c99c3a9284e493be632950b84cd789d08ed3e9d@golang.org>

nawawi/go,cloudflare/go,golang/go,golang/go,akutz/go,golang/go,akutz/go,golang/go,nawawi/go,CAFxX/go,CAFxX/go,cloudflare/go,cloudflare/go,golang/go,CAFxX/go,akutz/go,nawawi/go,golang/go,cloudflare/go,akutz/go,CAFxX/go,nawawi/go,CAFxX/go,cloudflare/go,akutz/go,CAFxX/go,nawawi/go,nawawi/go,CAFxX/go,akutz/go,akutz/go,CAFxX/go,cloudflare/go,nawawi/go,golang/go,nawawi/go,golang/go,akutz/go,cloudflare/go,cloudflare/go