c++: -frounding-math test [PR109359]

This test was fixed by the patch for PR95226, but that patch had no
testcase so let's add this one.

	PR c++/109359

gcc/testsuite/ChangeLog:

	* g++.dg/ext/frounding-math1.C: New test.

gcc/testsuite/g++.dg/ext/frounding-math1.C

@@ -0,0 +1,8 @@
+// PR c++/109359
+// { dg-additional-options -frounding-math }
+
+// For a while we were emitting two doubles (4 .long directives) as the value
+// of a float array; it should only be two .longs.
+
+// { dg-final { scan-assembler-times "long" 2 { target x86_64-*-* } } }
+float xs[] = {0.001914, 0.630539};