man page fixes

man/header.1

@@ -17,6 +17,12 @@ the VIPS extension block: the XML defining the image metadata. You can alter
 this, then reattach with 
 .B edvips(1).
 
+.TP
+.B -a, --all
+Show all fields. Normally 
+.B header
+just shows a one-line summary.
+
 .SH EXAMPLES
  $ header -f Xsize ~/pics/*.v   
  1024

man/vips.1

@@ -57,15 +57,15 @@ Run a vips8 operation. Operation options must follow the operation name.
 Get a "usage" message for an operation
 
   $ vips add 
-  VipsAdd (add), add two images
-    add left right out
+  usage:
+     add left right out
+     add two images
   where:
-    left :: VipsImage (input)
-    right :: VipsImage (input)
-    out :: VipsImage (output)
-  optional arguments:
-    imtest :: VipsImage (input)
-    booltest :: gboolean (input)
+     left         - Left-hand image argument, input VipsImage
+     right        - Right-hand image argument, input VipsImage
+     out          - Output image, output VipsImage
+  operation flags: sequential-unbuffered 
+  add: too few arguments
 
 .SH RETURN VALUE
 returns 0 on success and non-zero on error.

man/vipsthumbnail.1

@@ -55,7 +55,7 @@ The default value is
 meaning JPEG output, with
 .B tn_
 prepended. You can add format options too, for example
-.B tn_%s.jpg:20
+.B tn_%s.jpg[Q=20]
 will write JPEG images with Q set to 20.
 
 .TP