library: trade 'float' type for a 'double', <pids> api

While we really do not need the extra precision, we'll
trade that recently introduced float type for a double
for efficiency on a 64 bit platform. Additionally, the
UTILIZATION algorithm was tweaked producing less code.

The net result is four fewer machine instructions with
a reduction of 14 total bytes in that function's size.

Reference(s):
. introduced 'real' type & 'utilization' item
commit c69104b2b8

Signed-off-by: Jim Warner <james.warner@comcast.net>

proc/pids.h

@@ -214,7 +214,7 @@ struct pids_result {
         unsigned long long  ull_int;
         char               *str;
         char              **strv;
-        float               real;
+        double              real;
     } result;
 };