Add function glm_perspective_lh_zo

This commit adds the function `glm_perspective_lh_zo`, modelled on the
implementation of glm_perspective, but amended to provide a left-hand
coordinate system expected by DirectX, Metal and Vulkan (per the GLM
project's `glm/detail/setup.hpp`). It uses a clip-space of zero-to-one.

The function is tested against a longhand version of the algorithm it
seeks to implement as well as against the output of the GLM project's
`glm::perspectiveLH_ZO` function. This commit adds a new subdirectory
`test/glm_cmp` which contains a basic CMake file and `main.cpp`. An
interested user should link or copy or clone the GLM project into this
directory. The `main` function can be used to print the reference data
used so others can verify behaviour in the future, or add new literal
reference values.

test/src/test_cam.c

@@ -7,6 +7,40 @@
 
 #include "test_common.h"
 
+TEST_IMPL(perspective_lh_zo) {
+  mat4 dst;
+  const float fovy   = glm_rad(45.0f);
+  const float aspect = 640/480.0f;
+  const float near   = 0.1f;
+  const float far    = 100.0f;
+
+  glm_perspective_lh_zo(fovy, aspect, near, far, dst);
+
+  /* Sanity mk. I */
+  /* Longhand version of what the above function _should_ be doing */
+  ASSERT(test_eq(dst[0][0], 1 / (tanf(fovy / 2) * aspect)))
+  ASSERT(test_eq(dst[1][1], 1 / tanf(fovy / 2)))
+  ASSERT(test_eq(dst[2][2], far / (far - near)))
+  ASSERT(test_eq(dst[2][3], 1.0f))
+  ASSERT(test_eq(dst[3][2], -1 * far * near / (far - near)))
+
+  /* Sanity mk. II */
+  /* "Reference values" generated by GLM's glm::perspectiveLH_ZO */
+  mat4 cmp = {0};
+  cmp[0][0] = 1.8106601f;
+  cmp[1][1] = 2.4142134f;
+  cmp[2][2] = 1.0010010f;
+  cmp[2][3] = 1.0000000f;
+  cmp[3][2] = -0.1001001f;
+
+  for (uint32_t i = 0 ; i < 16 ; i++) {
+    uint32_t r = i%4, c = i/4;
+    ASSERT(fabsf(dst[r][c] - cmp[r][c]) < GLM_FLT_EPSILON)
+  }
+
+  TEST_SUCCESS
+}
+
 TEST_IMPL(camera_lookat) {
   mat4 view1, view2;
   vec3 center,