Added support for GL_TEXTURE_BORDER_COLOR and GL_CLAMP_TO_BORDER in
OpenGL/OpenGLES, Direct3D9 and Direct3D11 backends.
For integer textures in OpenGLES3 contexts these additional entry points
are available now:

void glTexParameterIivOES(enum target, enum pname, const int *params);
void glTexParameterIuivOES(enum target, enum pname, const uint *params);

void glGetTexParameterIivOES(enum target, enum pname, int *params);
void glGetTexParameterIuivOES(enum target, enum pname, uint *params);

void glSamplerParameterIivOES(uint sampler, enum pname, const int *params);
void glSamplerParameterIuivOES(uint sampler, enum pname, const uint *params);

void glGetSamplerParameterIivOES(uint sampler, enum pname, int *params);
void glGetSamplerParameterIuivOES(uint sampler, enum pname, uint *params);

BUG=angleproject:2890
TEST=angle_end2end_tests.TextureBorderClamp*

Change-Id: Iee3eeb399d8d7851b3b30694ad8f21a2111f5828
Reviewed-on: https://chromium-review.googlesource.com/c/1257824
Commit-Queue: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Geoff Lang <geofflang@chromium.org>
Reviewed-by: Jamie Madill <jmadill@chromium.org>