DEP: remove code for supporting GCC <4 in Mingw32CCompiler
DEP: remove code for supporting GCC <4 in Mingw32CCompiler

The last GCC 3.x release before 4.0 was 3.4 which was released 2004,
so 17 years ago.

Removes all code only used with those old toolchains.

pdebuyl/numpy,jakirkham/numpy,mhvk/numpy,numpy/numpy,charris/numpy,rgommers/numpy,pdebuyl/numpy,seberg/numpy,jakirkham/numpy,numpy/numpy,endolith/numpy,mhvk/numpy,endolith/numpy,rgommers/numpy,pdebuyl/numpy,mattip/numpy,numpy/numpy,anntzer/numpy,pdebuyl/numpy,jakirkham/numpy,numpy/numpy,mattip/numpy,seberg/numpy,charris/numpy,endolith/numpy,jakirkham/numpy,mattip/numpy,jakirkham/numpy,anntzer/numpy,mhvk/numpy,seberg/numpy,seberg/numpy,charris/numpy,rgommers/numpy,anntzer/numpy,mattip/numpy,charris/numpy,mhvk/numpy,anntzer/numpy,mhvk/numpy,rgommers/numpy,endolith/numpy