sokol: fix v -Wimpure-v examples/2048/

vlib/sokol/sgl/enums.c.v

@@ -0,0 +1,12 @@
+module sgl
+
+// SglError is C.sgl_error_t
+pub enum SglError {
+	no_error = C.SGL_NO_ERROR // 0
+	vertices_full = C.SGL_ERROR_VERTICES_FULL
+	uniforms_full = C.SGL_ERROR_UNIFORMS_FULL
+	commands_full = C.SGL_ERROR_COMMANDS_FULL
+	stack_overflow = C.SGL_ERROR_STACK_OVERFLOW
+	stack_underfloat = C.SGL_ERROR_STACK_UNDERFLOW
+	no_context = C.SGL_ERROR_NO_CONTEXT
+}