Rename procmacro2_unstable to procmacro2_semver_exempt
diff --git a/src/strnom.rs b/src/strnom.rs
index 2f9e73f..35acff7 100644
--- a/src/strnom.rs
+++ b/src/strnom.rs
@@ -9,18 +9,18 @@
 #[derive(Copy, Clone, Eq, PartialEq)]
 pub struct Cursor<'a> {
     pub rest: &'a str,
-    #[cfg(procmacro2_unstable)]
+    #[cfg(procmacro2_semver_exempt)]
     pub off: u32,
 }
 
 impl<'a> Cursor<'a> {
-    #[cfg(not(procmacro2_unstable))]
+    #[cfg(not(procmacro2_semver_exempt))]
     pub fn advance(&self, amt: usize) -> Cursor<'a> {
         Cursor {
             rest: &self.rest[amt..],
         }
     }
-    #[cfg(procmacro2_unstable)]
+    #[cfg(procmacro2_semver_exempt)]
     pub fn advance(&self, amt: usize) -> Cursor<'a> {
         Cursor {
             rest: &self.rest[amt..],