add support for loading PVR images

this is from Q3A for Dreamcast

cmake/renderer_common.cmake

@@ -6,6 +6,7 @@ set(RENDERER_COMMON_SOURCES
     ${SOURCE_DIR}/renderercommon/tr_image_jpg.c
     ${SOURCE_DIR}/renderercommon/tr_image_pcx.c
     ${SOURCE_DIR}/renderercommon/tr_image_png.c
+    ${SOURCE_DIR}/renderercommon/tr_image_pvr.c
     ${SOURCE_DIR}/renderercommon/tr_image_tga.c
     ${SOURCE_DIR}/renderercommon/tr_noise.c
     ${SOURCE_DIR}/renderercommon/puff.c