Use form name in complaint in dwarf2_record_block_entry_pc

This changes dwarf2_record_block_entry_pc to issue a complaint using
the form name rather than a value.  This seems more correct to me.

Approved-By: Simon Marchi <simon.marchi@efficios.com>

gdb/dwarf2/read.c

diff --git a/gdb/dwarf2/read.c b/gdb/dwarf2/read.c
index 30205f2..ab68320 100644
--- a/gdb/dwarf2/read.c
+++ b/gdb/dwarf2/read.c
@@ -9967,8 +9967,8 @@ dwarf2_record_block_entry_pc (struct die_info *die, struct block *block,
 	    {
 	      /* We could possibly handle signed constants, but this is out
 		 of spec, so for now, just complain and ignore it.  */
-	      complaint (_("Unhandled constant for DW_AT_entry_pc, value (%s)"),
-			 plongest (attr->as_nonnegative ()));
+	      complaint (_("Invalid form for DW_AT_entry_pc: %s"),
+			 dwarf_form_name (attr->form));
 	    }
 	}
       else