GLX misses a bunch of constants

[yoanlcq]

These are the constants I've found in my system GL/glx.h header which are not part of src/glx.rs and should be.

/*
 * Error codes returned by glXGetConfig:
 */
#define GLX_BAD_SCREEN      1
#define GLX_BAD_ATTRIBUTE   2
#define GLX_NO_EXTENSION    3
#define GLX_BAD_VISUAL      4
#define GLX_BAD_CONTEXT     5
#define GLX_BAD_VALUE           6
#define GLX_BAD_ENUM        7


/*
 * GLX 1.1 and later:
 */
#define GLX_VENDOR      1
#define GLX_VERSION     2
#define GLX_EXTENSIONS      3

// drawable type mask
#define GLX_AUX_BUFFERS_BIT     0x00000010
#define GLX_FRONT_LEFT_BUFFER_BIT   0x00000001
#define GLX_FRONT_RIGHT_BUFFER_BIT  0x00000002
#define GLX_BACK_LEFT_BUFFER_BIT    0x00000004
#define GLX_BACK_RIGHT_BUFFER_BIT   0x00000008
#define GLX_DEPTH_BUFFER_BIT        0x00000020
#define GLX_STENCIL_BUFFER_BIT      0x00000040
#define GLX_ACCUM_BUFFER_BIT        0x00000080

#define GLX_VISUAL_ID           0x800B
#define GLX_SCREEN          0x800C

#define GLX_RGBA_TYPE           0x8014
#define GLX_COLOR_INDEX_TYPE        0x8015
#define GLX_MAX_PBUFFER_WIDTH       0x8016
#define GLX_MAX_PBUFFER_HEIGHT      0x8017
#define GLX_MAX_PBUFFER_PIXELS      0x8018
#define GLX_PRESERVED_CONTENTS      0x801B
#define GLX_LARGEST_PBUFFER     0x801C
#define GLX_WIDTH           0x801D
#define GLX_HEIGHT          0x801E
#define GLX_EVENT_MASK          0x801F
#define GLX_DAMAGED         0x8020
#define GLX_SAVED           0x8021
#define GLX_WINDOW          0x8022
#define GLX_PBUFFER         0x8023
#define GLX_PBUFFER_HEIGHT              0x8040
#define GLX_PBUFFER_WIDTH               0x8041
#define GLX_PBUFFER_CLOBBER_MASK    0x08000000

/*
 * GLX 1.4 and later:
 */
#define GLX_SAMPLE_BUFFERS              0x186a0 /*100000*/
#define GLX_SAMPLES                     0x186a1 /*100001*/

[ghost]

Added in 44d9c74.