doc: Some fixes for the Cogl documentation

• 3 general fixes (typos, copy/paste),
 • ignore cogl-object-private.h,
 • cogl_fixed_atani() was in reality cogl_fixed_atan(), fixed in commit
   43564f05.
 • Fix the cogl-vector section: sections must have a </SECTION> tag at
   the end. Also the cogl-vector section was added in the middle of the
   cogl-buffer one. Let's shiffle it out and add that </SECTION> tag.

doc/reference/cogl/Makefile.am

@@ -74,6 +74,7 @@ IGNORE_HFILES=\
 	cogl-matrix-private.h 			\
 	cogl-matrix-stack.h 			\
 	cogl-spans.h 				\
+	cogl-object-private.h			\
 	cogl-pixel-buffer-private.h		\
 	cogl-profile.h				\
 	cogl-sub-texture-private.h		\

doc/reference/cogl/cogl-sections.txt

@@ -329,7 +329,7 @@ cogl_sqrti
 
 <SUBSECTION>
 cogl_fixed_atan2
-cogl_fixed_atani
+cogl_fixed_atan
 cogl_fixed_cos
 cogl_fixed_log2
 cogl_fixed_pow
@@ -508,6 +508,12 @@ cogl_is_pixel_buffer
 <SUBSECTION>
 cogl_texture_new_from_buffer
 
+<SUBSECTION Private>
+cogl_buffer_access_get_type
+cogl_buffer_update_hint_get_type
+cogl_buffer_usage_hint_get_type
+</SECTION>
+
 <SECTION>
 <FILE>cogl-vector</FILE>
 <TITLE>Vectors</TITLE>
@@ -527,9 +533,4 @@ cogl_vector3_magnitude
 cogl_vector3_cross_product
 cogl_vector3_dot_product
 cogl_vector3_distance
-
-<SUBSECTION Private>
-cogl_buffer_access_get_type
-cogl_buffer_update_hint_get_type
-cogl_buffer_usage_hint_get_type
 </SECTION>