Integrate perlio:

[  8927]
Change method names in Encode implementation classes to something
less confusing (preparing to "go public").

[  8926]
GCC __atribute__ / printf fix

[  8925]
Checked in the wrong one ...

[  8923]
Encode API documentation nd tidy up.
Minor additions to test.
Tweaks sv_utf8_upgrade() to force SvPV, and always SvUTF8_on and return length.
Adds STRLEN to standard typemap.

p4raw-link: @8927 on //depot/perlio: 50d2698546d7dba5ed48b29bf1c13887b041a4ba
p4raw-link: @8926 on //depot/perlio: c745e42cb33cb9fcfc4d47fe732cfa4725aa5d07
p4raw-link: @8925 on //depot/perlio: 2a936312a7ab627c98624c1ea83115246309b3d7
p4raw-link: @8923 on //depot/perlio: 4411f3b60960504e67715e05eb0ed3192bfff8fc

p4raw-id: //depot/perl@8934

diff --combined perl.h
index 1259f62,2b66473..a1ddcf0
--- 1/perl.h
--- 2/perl.h
+++ b/perl.h
@@@ -2209,7 -2209,7 +2209,7 @@@ struct ufuncs 
  /* In pre-5.7-Perls the 'U' magic didn't get the thread context.
   * XS code wanting to be backward compatible can do something
   * like the following:
-  
+ 
  #ifndef PERL_MG_UFUNC
  #define PERL_MG_UFUNC(name,ix,sv) I32 name(IV ix, SV *sv)
  #endif
@@@ -3332,8 -3332,12 +3332,12 @@@ typedef struct am_table_short AMTS
   * Remap printf
   */
  #undef printf
+ #ifdef __GNUC__
+ #define printf(fmt,args...) PerlIO_stdoutf(fmt,##args)
+ #else
  #define printf PerlIO_stdoutf
  #endif
+ #endif
  
  /* if these never got defined, they need defaults */
  #ifndef PERL_SET_CONTEXT
@@@ -3513,10 -3517,6 +3517,10 @@@
  #define EXEC_ARGV_CAST(x) x
  #endif
  
 +#ifdef EBCDIC
 +#define ALPHAS_HAVE_GAPS
 +#endif
 +
  /* and finally... */
  #define PERL_PATCHLEVEL_H_IMPLICIT
  #include "patchlevel.h"