Clarify that unrestricted doubles and floats include NaNs. (#393)

Closes https://www.w3.org/Bugs/Public/show_bug.cgi?id=29240.

index.bs

@@ -5121,7 +5121,7 @@ The [=type name=] of the
 
 The {{float}} type is a floating point numeric
 type that corresponds to the set of finite single-precision 32 bit
-IEEE 754 floating point numbers.  [[!IEEE-754]]
+IEEE 754 floating point numbers. [[!IEEE-754]]
 
 {{float}} constant values in IDL are
 represented with <emu-t class="regex"><a href="#prod-float">float</a></emu-t>
@@ -5143,7 +5143,7 @@ The [=type name=] of the
 
 The {{unrestricted float}} type is a floating point numeric
 type that corresponds to the set of all possible single-precision 32 bit
-IEEE 754 floating point numbers, finite and non-finite.  [[!IEEE-754]]
+IEEE 754 floating point numbers, finite, non-finite, and special "not a number" values (NaNs). [[!IEEE-754]]
 
 {{unrestricted float}} constant values in IDL are
 represented with <emu-t class="regex"><a href="#prod-float">float</a></emu-t>
@@ -5157,7 +5157,7 @@ The [=type name=] of the
 
 The {{double}} type is a floating point numeric
 type that corresponds to the set of finite double-precision 64 bit
-IEEE 754 floating point numbers.  [[!IEEE-754]]
+IEEE 754 floating point numbers. [[!IEEE-754]]
 
 {{double}} constant values in IDL are
 represented with <emu-t class="regex"><a href="#prod-float">float</a></emu-t>
@@ -5171,7 +5171,7 @@ The [=type name=] of the
 
 The {{unrestricted double}} type is a floating point numeric
 type that corresponds to the set of all possible double-precision 64 bit
-IEEE 754 floating point numbers, finite and non-finite.  [[!IEEE-754]]
+IEEE 754 floating point numbers, finite, non-finite, and special "not a number" values (NaNs). [[!IEEE-754]]
 
 {{unrestricted double}} constant values in IDL are
 represented with <emu-t class="regex"><a href="#prod-float">float</a></emu-t>