Test boost/extract_rep*_02: adjust test output for libc++

Test boost/extract_rep*_02: adjust test output for libc++

We have to adjust the output after
bfe81e2b89a39792ee48dd7d028e8860cc44551e also for the libc++ variant.

See 9038e6000b681910227e24302e964835a344ddf8

For reference, the difference between libstdc++ and libc++ output is as
follows:
```
--- extract_representative_set_02.with_p4est=true.mpirun=3.output       2020-05-15 09:27:53.256578723 -0500
+++ extract_representative_set_02.with_p4est=true.mpirun=3.output.libstdc++     2020-05-15 09:58:47.149994734 -0500
@@ -137,16 +137,16 @@
 0.5 -0.707107

 DEAL:1::-0.0732233 -0.0732233
-0.21967 -0.0732233
-0.21967 0.292893
+0.292893 -0.0732233
+0.292893 0.292893
 -0.0732233 0.292893
 -0.0732233 -0.0732233

-DEAL:1::0.21967 -1.11022e-16
-1 -1.11022e-16
+DEAL:1::0.21967 -0.0732233
+1 -0.0732233
 1 0.382683
 0.21967 0.382683
-0.21967 -1.11022e-16
+0.21967 -0.0732233
```