Make CONFIG_COLORSPACE_HEADERS public API changes unconditional.

Avoid changing the public API based on an experiment flag:

- Remove aom_config.h include from aom_image.h.
- Unconditionally include the existing API additions.
- Add some missing doc comments (silences Doxygen warnings).
- Return an error when using ctrl flags that require
  CONFIG_COLORSPACE_HEADERS when it's not enabled.
- Move colorspace_headers to the correct section of configure.
- Move CONFIG_COLORSPACE_HEADERS to the correct section of
  aom_config_defaults.cmake.
- clang-format style check appeasement

Change-Id: I7b5d72c6f9f1a5561409d7813ba59180d98d8805
diff --git a/aom/aom_image.h b/aom/aom_image.h
index 34cf715..d8817b8 100644
--- a/aom/aom_image.h
+++ b/aom/aom_image.h
@@ -35,8 +35,6 @@
 #define AOM_IMG_FMT_HAS_ALPHA 0x400    /**< Image has an alpha channel. */
 #define AOM_IMG_FMT_HIGHBITDEPTH 0x800 /**< Image uses 16bit framebuffer. */
 
-#include "./aom_config.h"
-
 /*!\brief List of supported image formats */
 typedef enum aom_img_fmt {
   AOM_IMG_FMT_NONE,
@@ -71,25 +69,19 @@
 
 /*!\brief List of supported color spaces */
 typedef enum aom_color_space {
-  AOM_CS_UNKNOWN = 0,   /**< Unknown */
-  AOM_CS_BT_601 = 1,    /**< BT.601 */
-  AOM_CS_BT_709 = 2,    /**< BT.709 */
-  AOM_CS_SMPTE_170 = 3, /**< SMPTE.170 */
-  AOM_CS_SMPTE_240 = 4, /**< SMPTE.240 */
-#if CONFIG_COLORSPACE_HEADERS
+  AOM_CS_UNKNOWN = 0,     /**< Unknown */
+  AOM_CS_BT_601 = 1,      /**< BT.601 */
+  AOM_CS_BT_709 = 2,      /**< BT.709 */
+  AOM_CS_SMPTE_170 = 3,   /**< SMPTE.170 */
+  AOM_CS_SMPTE_240 = 4,   /**< SMPTE.240 */
   AOM_CS_BT_2020_NCL = 5, /**< BT.2020 non-constant luminance (BT.2100) */
   AOM_CS_BT_2020_CL = 6,  /**< BT.2020 constant luminance */
   AOM_CS_SRGB = 7,        /**< sRGB */
   AOM_CS_ICTCP = 8,       /**< ICtCp, ITU-R BT.2100 */
   AOM_CS_RESERVED = 9     /**< Values 9..31 are reserved */
-#else
-  AOM_CS_BT_2020 = 5,  /**< BT.2020 */
-  AOM_CS_RESERVED = 6, /**< Reserved */
-  AOM_CS_SRGB = 7      /**< sRGB */
-#endif
-} aom_color_space_t; /**< alias for enum aom_color_space */
+} aom_color_space_t;      /**< alias for enum aom_color_space */
 
-#if CONFIG_COLORSPACE_HEADERS
+/*!\brief List of supported transfer functions */
 typedef enum aom_transfer_function {
   AOM_TF_UNKNOWN = 0,      /**< Unknown */
   AOM_TF_BT_709 = 1,       /**< BT.709 */
@@ -97,7 +89,6 @@
   AOM_TF_HLG = 3,          /**< Hybrid Log-Gamma */
   AOM_TF_RESERVED = 4      /**< Values 4..31 are reserved */
 } aom_transfer_function_t; /**< alias for enum aom_transfer_function */
-#endif
 
 /*!\brief List of supported color range */
 typedef enum aom_color_range {
@@ -105,7 +96,7 @@
   AOM_CR_FULL_RANGE = 1    /**< YUV/RGB [0..255] */
 } aom_color_range_t;       /**< alias for enum aom_color_range */
 
-#if CONFIG_COLORSPACE_HEADERS
+/*!\brief List of chroma sample positions */
 typedef enum aom_chroma_sample_position {
   AOM_CSP_UNKNOWN = 0,          /**< Unknown */
   AOM_CSP_VERTICAL = 1,         /**< Horizontally co-located with luma(0, 0)*/
@@ -113,17 +104,14 @@
   AOM_CSP_COLOCATED = 2,        /**< Co-located with luma(0, 0) sample */
   AOM_CSP_RESERVED = 3          /**< Reserved value */
 } aom_chroma_sample_position_t; /**< alias for enum aom_transfer_function */
-#endif
 
 /**\brief Image Descriptor */
 typedef struct aom_image {
-  aom_img_fmt_t fmt;    /**< Image Format */
-  aom_color_space_t cs; /**< Color Space */
-#if CONFIG_COLORSPACE_HEADERS
+  aom_img_fmt_t fmt;                /**< Image Format */
+  aom_color_space_t cs;             /**< Color Space */
   aom_transfer_function_t tf;       /**< transfer function */
   aom_chroma_sample_position_t csp; /**< chroma sample position */
-#endif
-  aom_color_range_t range; /**< Color Range */
+  aom_color_range_t range;          /**< Color Range */
 
   /* Image storage dimensions */
   unsigned int w;         /**< Stored image width */