Bump stdpp.

6 jobs for master in 9 minutes and 10 seconds (queued for 1 second)
Name Stage Failure
failed
build-coq.8.8.2 Build
Makefile.coq:317: recipe for target 'all' failed
make[1]: *** [all] Error 2
Makefile:6: recipe for target 'all' failed
make: *** [all] Error 2

real 1m40.301s
user 4m31.508s
sys 0m21.732s
ERROR: Job failed: exit code 1
failed
build-coq.dev Build
Makefile.coq:319: recipe for target 'all' failed
make[1]: *** [all] Error 2
Makefile:6: recipe for target 'all' failed
make: *** [all] Error 2

real 1m35.737s
user 4m7.184s
sys 0m21.652s
ERROR: Job failed: exit code 1
failed
build-coq.8.7.1 Build
Makefile.coq:317: recipe for target 'all' failed
make[1]: *** [all] Error 2
Makefile:6: recipe for target 'all' failed
make: *** [all] Error 2

real 1m27.425s
user 3m51.116s
sys 0m22.728s
ERROR: Job failed: exit code 1
failed
build-coq.8.7.2 Build
Makefile.coq:318: recipe for target 'all' failed
make[1]: *** [all] Error 2
Makefile:6: recipe for target 'all' failed
make: *** [all] Error 2

real 1m35.909s
user 4m14.868s
sys 0m22.800s
ERROR: Job failed: exit code 1
failed
build-coq.8.8.0 Build
Makefile.coq:317: recipe for target 'all' failed
make[1]: *** [all] Error 2
Makefile:6: recipe for target 'all' failed
make: *** [all] Error 2

real 1m25.359s
user 3m40.736s
sys 0m20.696s
ERROR: Job failed: exit code 1
failed
build-coq.8.9.0 Build
Makefile.coq:326: recipe for target 'all' failed
make[1]: *** [all] Error 2
Makefile:6: recipe for target 'all' failed
make: *** [all] Error 2

real 1m26.574s
user 3m43.780s
sys 0m20.288s
ERROR: Job failed: exit code 1