Document the tftp.blksize variable added in src/lib/libstand/tftp.c.

Approved by: re	(kib)
Requested by: maxim

sys/boot/forth/loader.conf

@@ -55,6 +55,11 @@ module_path="/boot/modules"	# Set the module search path
 #prompt="\\${interpret}"	# Set the command prompt
 #root_disk_unit="0"		# Force the root disk unit number
 #rootdev="disk1s1a"		# Set the root filesystem
+#tftp.blksize="1428"		# Set the RFC 2348 TFTP block size.
+				# If the TFTP server does not support RFC 2348,
+				# the block size is set to 512.  If the value
+				# is out of range ( < 8 || > 9008 ) an error is
+				# returned.
 
 
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