configure: C++11 handling for NTL #4
Description
NTL may be configured with C++11 features. This is the default in NTL 11.
In this case, currently configure does not find NTL. Two options:
- Try to find C++11 compiler switches just in case that NTL has been configured as such.
- Detect if NTL has been configured with C++11 features, and only then find C++11 compiler switch.