#46 configure script doesn't fully implement compiler choice

[Vince McIntyre]

I tried to build healpix specifying {gfortran,gcc,g++}-4.3 instead of the system default (-4.4, which has a known issue (#45)). This worked only partially.

First I configured F90 compilation, then C, then C++. In the C++ compilation I did not get the opportunity to enter 'g++-4.3' as the compiler, I selected 'basic_gcc' when it was offered.

After configuring everything I typed 'make' it started to build with the default g++ and gcc. To fix I had to edit src/cxx/config/config.basic_gcc. Then everything built and tested out ok. The F90 config was correct without me doing anything.