[petsc-dev] use --with-single-library=1 as default?

[Satish Balay]

Should we default to using --with-single-library=1? [I'd prefer this -
as it will minimize dlopen issues from external packages.]

Also - I'd like to have distinct library names between
--with-single-library=0 and 1 - so that there is no ambiguity.

i.e libpetsc.a for --with-single-library=1
libpetscsys.a [instead of current libpetsc.a] for --with-single-library=0

With this change, the 'shared' targets don't have to be overloaded for
libpetsc.so [for eg: for shared_darwin]

Satish