Use distinct types for RealInfinity

[putianyi889]

This change will make it easier to handle ambiguities and conflicts. Old interface is reserved, except for x.signbit fully replaced by signbit(x).

• #5

[codecov[bot]]

Codecov Report

Patch coverage: 100.00% and no project coverage change.

Comparison is base (0972ead) 99.14% compared to head (cb8e5d9) 99.15%.

Additional details and impacted files

@@           Coverage Diff           @@
##           master      #37   +/-   ##
=======================================
  Coverage   99.14%   99.15%           
=======================================
  Files           2        2           
  Lines         350      353    +3     
=======================================
+ Hits          347      350    +3     
  Misses          3        3           

Impacted Files	Coverage Δ
src/Infinities.jl	99.55% <100.00%> (+<0.01%)	:arrow_up:

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[nsajko]

Wouldn't this be a breaking change? Why not just introduce new types, and keep RealInfinity as is?