Doc: fix minor typos in two ECPG function descriptions.

Noted by Aidar Imamov.

Discussion: https://postgr.es/m/170869935022.643.3709087848818148291@wrigleys.postgresql.org

doc/src/sgml/ecpg.sgml

@@ -8847,7 +8847,7 @@ int dectodbl(decimal *np, double *dblp);
       <term><function>dectoint</function></term>
       <listitem>
        <para>
-        Convert a variable to type decimal to an integer.
+        Convert a variable of type decimal to an integer.
 <synopsis>
 int dectoint(decimal *np, int *ip);
 </synopsis>
@@ -8873,7 +8873,7 @@ int dectoint(decimal *np, int *ip);
       <term><function>dectolong</function></term>
       <listitem>
        <para>
-        Convert a variable to type decimal to a long integer.
+        Convert a variable of type decimal to a long integer.
 <synopsis>
 int dectolong(decimal *np, long *lngp);
 </synopsis>