Add C89 support

Allow compilation from C89 compilers.

Changelog

@@ -0,0 +1,48 @@
+Changelog
+=========
+
+version 0.4.1:
+- changed license to MIT
+- fixed compilation errors
+- fixed lighting bug
+- fixed color conversions
+
+version 0.4:
+  - added 24/32 bit rendering support (Olivier Landemarre - F. Bellard)
+  - fixed GL_TRIANGLE_STRIP (Olivier Landemarre)
+- added gl_malloc, gl_free, gl_zalloc wrappers (Olivier Landemarre)
+
+  version 0.3:
+  - added NanoX API (nglx) (F. Bellard)
+- added gears example and unified GUI in examples (F. Bellard)
+  - added TGL_FEATURE_RENDER_BITS so that it will be possible to render
+  natively in 15/16/24 or 32 bits. (F. Bellard)
+  - interpolated lines (Olivier Landemarre)
+  - fast no shading case (Olivier Landemarre)
+- fast no projection case (Olivier Landemarre)
+
+  version 0.2: Fabrice Bellard
+  - added 24/32 bpp support. Added some features.h ifdefs.
+  - fixed some error reporting cases in the examples
+- endianness is deduced from the glibc (BYTE_ORDER macro)
+
+  version 0.19: Peder Blekken
+  - new files BeOS/* src/msghandling.*, src/arrays.*, src/oscontext.c
+                     include/GL/oscontext.h src/features.h
+                     - added support for BeOS, see README.BEOS
+                     - added support for drawing convex polygons with unlimited # of vertices
+                     - added support for GL_LIGHT_MODEL_TWO_SIDE
+                     - added generic rotation code for glopRotate
+                     - added support for opengl 1.1 arrays
+                     - added support for glPolygonOffset, not implemented.
+                     - added glGetFloatv, limited support.
+                     - added some pnames for glGetIntegerv
+                     - added some empty functions in include/GL/gl.h to compile VRMLView
+                     - added GL_VERSION_1_1 define in include/GL/gl.h
+                     - fixed "bug" when context->gl_resize_viewport is not set.
+                     - fixed bug in glBindTexture (didn't accept texture object 0)
+
+                     version 0.1:
+                     - Initial revision, Fabrice Bellard
+
+--- end of Changelog ---