all: format code according to Go 1.19 rules

Go 1.19 started reformatting code in a way that makes it more obvious
how it will be rendered on pkg.go.dev. It gets it almost right, but not
entirely. Therefore, I had to modify some of the comments so that they
are formatted correctly.

src/runtime/runtime.go

@@ -44,6 +44,7 @@ func memzero(ptr unsafe.Pointer, size uintptr)
 // This intrinsic returns the current stack pointer.
 // It is normally used together with llvm.stackrestore but also works to get the
 // current stack pointer in a platform-independent way.
+//
 //export llvm.stacksave
 func stacksave() unsafe.Pointer
 
@@ -70,6 +71,7 @@ func nanotime() int64 {
 }
 
 // Copied from the Go runtime source code.
+//
 //go:linkname os_sigpipe os.sigpipe
 func os_sigpipe() {
 	runtimePanic("too many writes on closed pipe")