Allow 'Infinity' and '-Infinity' as input to the float4 and float8

types. Update the regression tests and the documentation to reflect
this. Remove the UNSAFE_FLOATS #ifdef.

This is only half the story: we still unconditionally reject
floating point operations that result in +/- infinity. See
recent thread on -hackers for more information.

doc/src/sgml/syntax.sgml

@@ -1,5 +1,5 @@
 <!--
-$PostgreSQL: pgsql/doc/src/sgml/syntax.sgml,v 1.89 2003/11/29 19:51:37 pgsql Exp $
+$PostgreSQL: pgsql/doc/src/sgml/syntax.sgml,v 1.90 2004/03/12 00:25:40 neilc Exp $
 -->
 
 <chapter id="sql-syntax">
@@ -359,6 +359,23 @@ SELECT 'foo'      'bar';
 </literallayout>
     </para>
 
+    <para>
+     In addition, there are several special constant values that are
+     accepted as numeric constants. The <type>float4</type> and
+     <type>float8</type> types allow the following special constants:
+<literallayout>
+Infinity
+-Infinity
+NaN
+</literallayout>
+     These represent the IEEE 754 special values
+     <quote>infinity</quote>, <quote>negative infinity</quote>, and
+     <quote>not-a-number</quote>, respectively. The
+     <type>numeric</type> type only allows <literal>NaN</>, whereas
+     the integral types do not allow any of these constants. Note that
+     these constants are recognized in a case-insensitive manner.
+    </para>
+
     <para>
      <indexterm><primary>integer</primary></indexterm>
      <indexterm><primary>bigint</primary></indexterm>