fix for flint compiling issues

Hello Dan,


here is the final fix proposal
I removed the MP patch( differing between mpir and gmp), since Flint cannot really handle mpir 
(it looks only for gmp includes). So if  the user wants mpir, he has to compile the M2-shipped mpir.

Then we have to 'override' the default lookup path `/usr/local/` for gmp/mpir, gc, mpfr, ntl by 
`$(LIBRARIESDIR)/lib` . For that the `-L$(LIBRARIESDIR)/lib` -entry has to be the first one in the "LIBS"- variable of Flints Makefile ; therefore I added `LIB_DIRS=$(LIBRARIESDIR)/lib` instead of `EXTRA_LIB_DIRS=$(LIBRARIESDIR)/lib` 

Finally I added the --with-blas flag and hope that Flint will gain some performance (I didn't check for performance)

Correcting the lpthread link order we discussed already.


Jakob