Erlang 27 compat: special case 0.0 (positive and negative) w/o using matching

Erlang 27 erlc requires us to match on both but earlier versions
complain that one head of the function is unreachable because the other
one always matches.

So we avoid pattern matching entirely.

(cherry picked from commit 5903ff6)
(cherry picked from commit 24c9da9)

Author: michaelklishin

deps/rabbit_common/src/rabbit_numerical.erl

@@ -30,9 +30,7 @@
 %%       human-readable output, or compact ASCII serializations for floats.
 digits(N) when is_integer(N) ->
     integer_to_list(N);
-digits(+0.0) ->
-    "0.0";
-digits(-0.0) ->
+digits(N) when N =:= 0.0 ->
     "0.0";
 digits(Float) ->
     {Frac1, Exp1} = frexp_int(Float),