FindPETSc: Fixed paths and library names on windows

If PETSc static libs (/MT, static) disagree with existing library flags
(/MD, dynamic), we issue a warning telling the user to choose a
compatible compilation mode.

Windows library paths need not start with "/", requiring more permissive
regex patterns.

Squashed-by: Jed Brown <jed@59A2.org>
Added . to lib detection regex
Merge branch 'master' of https://github.com/jedbrown/cmake-modules
FindPETSc.cmake: Added PETSC_INCPATH and PETSC_LIBPATH search paths

In the event that you try to copy a PETSc installation between two
non-identical machines, many of the paths to external libraries will be
incorrect.  These two variables allow you to specify search paths so
that FindPETSc will succeed.  The variables are:

* PETSC_INCPATH - A list of strings containing the include paths to be
   searched

* PETSC_LIBPATH - A list of strings containing the library paths to be
   searched