cpp: cmake: Don't enable -pedantic if it breaks long long use

GCC 4.2 doesn't support `long long` in `-pedantic` mode due to it not being part of the C++98 standard.  This patch only enables `-pedantic` if `long long` works.  For later compilers this isn't a problem, and the updated test won't change anything.

Testing: this should make http://ci.openmicroscopy.org/view/5.1/job/BIOFORMATS-5.1-merge-cpp/label=10.12.2.157/ go green.  If it doesn't, then the check isn't correct or there are additional portability issues to resolve for this node.

This PR addresses this specific problem:
```
/Users/ome/hudson/workspace/BIOFORMATS-5.1-merge-cpp/label/10.12.2.157/gtest/include/gtest/internal/gtest-port.h:1649: error: ISO C++ does not support 'long long'
```
If that error is missing, then this change is working.  You should see:
```
cd /Users/ome/hudson/workspace/BIOFORMATS-5.1-merge-cpp/label/10.12.2.157/build/cpp/test && /usr/bin/c++    -std=c++98 -pedantic -Wall -Wcast-align -Wwrite-strings -Wswitch-default -Wcast-qual -Wunused-variable -Wredundant-decls -Wctor-dtor-privacy -Wnon-virtual-dtor -Wreorder -Wold-style-cast -Woverloaded-virtual -fstrict-aliasing -I/Users/ome/hudson/workspace/BIOFORMATS-5.1-merge-cpp/label/10.12.2.157/gtest/include    -o CMakeFiles/testmain.dir/main.cpp.o -c /Users/ome/hudson/workspace/BIOFORMATS-5.1-merge-cpp/label/10.12.2.157/bioformats/cpp/test/main.cpp
```
with the `-pedantic` removed.