Doc: wording tweak for PERL, PYTHON, TCLSH configuration variables.

Replace "Full path to ..." with "Full path name of ...".  At least one
user has misinterpreted the existing wording as meaning "Directory
containing ...".

doc/src/sgml/installation.sgml

@@ -1422,7 +1422,7 @@ su - postgres
        <term><envar>PERL</envar></term>
        <listitem>
         <para>
-         Full path to the Perl interpreter.  This will be used to
+         Full path name of the Perl interpreter.  This will be used to
          determine the dependencies for building PL/Perl.
         </para>
        </listitem>
@@ -1432,7 +1432,7 @@ su - postgres
        <term><envar>PYTHON</envar></term>
        <listitem>
         <para>
-         Full path to the Python interpreter.  This will be used to
+         Full path name of the Python interpreter.  This will be used to
          determine the dependencies for building PL/Python.  Also,
          whether Python 2 or 3 is specified here (or otherwise
          implicitly chosen) determines which variant of the PL/Python
@@ -1449,7 +1449,7 @@ su - postgres
        <term><envar>TCLSH</envar></term>
        <listitem>
         <para>
-         Full path to the Tcl interpreter.  This will be used to
+         Full path name of the Tcl interpreter.  This will be used to
          determine the dependencies for building PL/Tcl, and it will
          be substituted into Tcl scripts.
         </para>