Add back support for shadow mapping, that CMU students removed

panda/src/gobj/shader.cxx

@@ -1262,6 +1262,8 @@ cg_parameter_type(CGparameter p) {
     case CG_SAMPLER3D:      return Shader::SAT_sampler3d;
     case CG_SAMPLER2DARRAY: return Shader::SAT_sampler2dArray;
     case CG_SAMPLERCUBE:    return Shader::SAT_samplercube;
+    case CG_SAMPLER1DSHADOW:return Shader::SAT_sampler1d;
+    case CG_SAMPLER2DSHADOW:return Shader::SAT_sampler2d;
     default: return SAT_unknown;
     }
   case CG_PARAMETERCLASS_ARRAY: return SAT_unknown;