UPBGE: Add full support of inverse before GLSL 140 in shaders.

Previously only inverse(mat4) was implemented if the GLSL version was under 140.
Now as this implementation is also used by custom shaders, the other inverse
overloads shoudl be implemented.

So the full version from https://github.com/stackgl/glsl-inverse/blob/master/index.glsl
is copied.

source/blender/gpu/shaders/gpu_shader_lib.glsl

@@ -3,6 +3,31 @@
  * copied from https://github.com/stackgl/glsl-inverse/blob/master/index.glsl
  */
 
+float inverse(float m) {
+  return 1.0 / m;
+}
+
+mat2 inverse(mat2 m) {
+  return mat2(m[1][1],-m[0][1],
+             -m[1][0], m[0][0]) / (m[0][0]*m[1][1] - m[0][1]*m[1][0]);
+}
+
+mat3 inverse(mat3 m) {
+  float a00 = m[0][0], a01 = m[0][1], a02 = m[0][2];
+  float a10 = m[1][0], a11 = m[1][1], a12 = m[1][2];
+  float a20 = m[2][0], a21 = m[2][1], a22 = m[2][2];
+
+  float b01 = a22 * a11 - a12 * a21;
+  float b11 = -a22 * a10 + a12 * a20;
+  float b21 = a21 * a10 - a11 * a20;
+
+  float det = a00 * b01 + a01 * b11 + a02 * b21;
+
+  return mat3(b01, (-a22 * a01 + a02 * a21), (a12 * a01 - a02 * a11),
+              b11, (a22 * a00 - a02 * a20), (-a12 * a00 + a02 * a10),
+              b21, (-a21 * a00 + a01 * a20), (a11 * a00 - a01 * a10)) / det;
+}
+
 mat4 inverse(mat4 m) {
 	float a00 = m[0][0], a01 = m[0][1], a02 = m[0][2], a03 = m[0][3],
 	a10 = m[1][0], a11 = m[1][1], a12 = m[1][2], a13 = m[1][3],