elfcpp/:

* elfcpp.h (PN_XNUM): Define.
gold/:
	* output.cc (Output_section_headers::do_sized_write): Write large
	segment count to sh_info field.
	(Output_file_header::do_sized_write): For large segment count,
	write PN_XNUM to e_phnum field.

elfcpp/elfcpp.h

@@ -302,6 +302,15 @@ enum EM
   // Old MN10200 objects used 0xdead (EM_MN10200 is correct).
 };
 
+// A special value found in the Ehdr e_phnum field.
+
+enum
+{
+  // Number of program segments stored in sh_info field of first
+  // section headre.
+  PN_XNUM = 0xffff
+};
+
 // Special section indices.
 
 enum