Minimize repetition in IO::Spec::*

Add a specific section in IO::Spec document with caveats about its
sub-classes.
Replace these caveats's mentions in IO::Spec::* documents by a reference
to IO::Spec document.

Author: stoned

doc/Type/IO/Spec.pod6

@@ -14,11 +14,13 @@ The sub-classes are documented separately, with the platform-specific
 differences documented in L<IO::Spec::Cygwin|/type/IO::Spec::Cygwin>, L<IO::Spec::QNX|/type/IO::Spec::QNX>,
 L<IO::Spec::Unix|/type/IO::Spec::Unix> and L<IO::Spec::Win32|/type/IO::Spec::Win32>.
 
-B<NOTE:> the C<IO::Spec::*> classes provide low-level path operations. Unless
+=head1 About sub-classes IO::Spec::*
+
+The C<IO::Spec::*> classes provide low-level path operations. Unless
 you're creating your own high-level path manipulation routines, you don't
 need to use C<IO::Spec::*>. Use L«C<IO::Path>|/type/IO::Path» instead.
 
-B<NOTE2:> no special validation is done by these classes (e.g. check whether
+Beware that no special validation is done by these classes (e.g. check whether
 path contains a null character). It is the job of higher-level classes, like
 L«C<IO::Path>|/type/IO::Path», to do that.
 

doc/Type/IO/Spec/Cygwin.pod6

@@ -9,14 +9,8 @@
 An object of this type is available via the variable C<$*SPEC> if the
 Raku interpreter is running on C<Cygwin>.
 
-The C<IO::Spec::*> classes provide low-level path operations. Unless
-you're creating your own high-level path manipulation routines, you
-don't need to use C<IO::Spec::*>. Use L«C<IO::Path>|/type/IO::Path»
-instead.
-
-Beware that no special validation is done by these classes (e.g. check
-whether path contains a null character). It is the job of higher-level
-classes, like L«C<IO::Path>|/type/IO::Path», to do that.
+About this class and its related classes also see
+L<IO::Spec|/type/IO::Spec>.
 
 =head1 Methods
 

doc/Type/IO/Spec/QNX.pod6

@@ -9,14 +9,8 @@
 An object of this type is available via the variable C<$*SPEC> if the
 Raku interpreter is running on a C<QNX> platform.
 
-The C<IO::Spec::*> classes provide low-level path operations. Unless
-you're creating your own high-level path manipulation routines, you
-don't need to use C<IO::Spec::*>. Use L«C<IO::Path>|/type/IO::Path»
-instead.
-
-Beware that no special validation is done by these classes (e.g. check
-whether path contains a null character). It is the job of higher-level
-classes, like L«C<IO::Path>|/type/IO::Path», to do that.
+About this class and its related classes also see
+L<IO::Spec|/type/IO::Spec>.
 
 =head1 Methods
 

doc/Type/IO/Spec/Unix.pod6

@@ -9,14 +9,8 @@
 An object of this type is available via the variable C<$*SPEC> if the
 Raku interpreter is running on a Unix-like platform.
 
-The C<IO::Spec::*> classes provide low-level path operations. Unless
-you're creating your own high-level path manipulation routines, you
-don't need to use C<IO::Spec::*>. Use L«C<IO::Path>|/type/IO::Path»
-instead.
-
-Beware that no special validation is done by these classes (e.g. check
-whether path contains a null character). It is the job of higher-level
-classes, like L«C<IO::Path>|/type/IO::Path», to do that.
+About this class and its related classes also see
+L<IO::Spec|/type/IO::Spec>.
 
 =head1 Methods
 

doc/Type/IO/Spec/Win32.pod6

@@ -9,14 +9,8 @@
 An object of this type is available via the variable C<$*SPEC> if the
 Raku interpreter is running on a Windows-like platform.
 
-The C<IO::Spec::*> classes provide low-level path operations. Unless
-you're creating your own high-level path manipulation routines, you
-don't need to use C<IO::Spec::*>. Use L«C<IO::Path>|/type/IO::Path»
-instead.
-
-Beware that no special validation is done by these classes (e.g. check
-whether path contains a null character). It is the job of higher-level
-classes, like L«C<IO::Path>|/type/IO::Path», to do that.
+About this class and its related classes also see
+L<IO::Spec|/type/IO::Spec>.
 
 =head1 Methods