diagind(A,k): empty range for k == -size(A,1) and k == size(A,2).
Add frexp to BigFloats, closes #7467

Kudos to @quinnj who noticed it
Fix reverse(r::FloatingPoint)

Related to #7420

Added test for reverse(r::FloatRange)
Add Lyapunov/Sylvester solver to NEWS. (#7435)
Merge pull request #7484 from ivarne/patch-4

Fix reverse(r::FloatingPoint)
Merge pull request #7477 from andrioni/frexp

Add frexp to BigFloats, closes #7467