Update config.h to pyconfig.h.

README

@@ -305,7 +305,7 @@ HP-UX:	Please read the file Misc/HPUX-NOTES for shared libraries.
 	When using threading, you may have to add -D_REENTRANT to the
 	OPT variable in the top-level Makefile; reported by Pat Knight,
 	this seems to make a difference (at least for HP-UX 10.20)
-	even though config.h defines it.
+	even though pyconfig.h defines it.
 
 HP PA-RISC 2.0: A recent bug report (http://www.python.org/sf/546117)
 	suggests that the C compiler in this 64-bit system has bugs