Increase negative GLSL coverage

Increase negative GLSL coverage

GLSL and ESSL specify that the following are legal declarations:
  int;
  int ,a;
while the following are not:
  struct foo { int; };
  struct bar { int ,a; };
  int a,;

Components: OpenGL

VK-GL-CTS issue: 7

Affects:
KHR-GL33.shaders.declarations.*
KHR-GLES3.shaders.declarations.*

Change-Id: Ib1735ca96e4ce7be60fa0ca91c64f7392b237605