Drop support for compilers without i128
diff --git a/build.rs b/build.rs
deleted file mode 100644
index a0474a4..0000000
--- a/build.rs
+++ /dev/null
@@ -1,48 +0,0 @@
-use std::env;
-use std::process::Command;
-use std::str::{self, FromStr};
-
-// The rustc-cfg strings below are *not* public API. Please let us know by
-// opening a GitHub issue if your build environment requires some way to enable
-// these cfgs other than by executing our build script.
-fn main() {
-    let minor = match rustc_minor_version() {
-        Some(minor) => minor,
-        None => return,
-    };
-
-    // 128-bit integers stabilized in Rust 1.26:
-    // https://blog.rust-lang.org/2018/05/10/Rust-1.26.html
-    if minor >= 26 {
-        println!("cargo:rustc-cfg=integer128");
-    }
-}
-
-fn rustc_minor_version() -> Option<u32> {
-    let rustc = match env::var_os("RUSTC") {
-        Some(rustc) => rustc,
-        None => return None,
-    };
-
-    let output = match Command::new(rustc).arg("--version").output() {
-        Ok(output) => output,
-        Err(_) => return None,
-    };
-
-    let version = match str::from_utf8(&output.stdout) {
-        Ok(version) => version,
-        Err(_) => return None,
-    };
-
-    let mut pieces = version.split('.');
-    if pieces.next() != Some("rustc 1") {
-        return None;
-    }
-
-    let next = match pieces.next() {
-        Some(next) => next,
-        None => return None,
-    };
-
-    u32::from_str(next).ok()
-}
diff --git a/src/ident_fragment.rs b/src/ident_fragment.rs
index a727152..5636455 100644
--- a/src/ident_fragment.rs
+++ b/src/ident_fragment.rs
@@ -69,10 +69,7 @@
 }
 
 ident_fragment_display!(bool, str, String);
-ident_fragment_display!(u8, u16, u32, u64, usize);
-
-#[cfg(integer128)]
-ident_fragment_display!(u128);
+ident_fragment_display!(u8, u16, u32, u64, u128, usize);
 
 // XXX: Should we implement `IdentFragment` for signed integers? It's a touch
 // inconvenient that the default inferred type for integer literals isn't a
diff --git a/src/to_tokens.rs b/src/to_tokens.rs
index 9d221b2..0f507c8 100644
--- a/src/to_tokens.rs
+++ b/src/to_tokens.rs
@@ -133,24 +133,20 @@
     i16 => i16_suffixed
     i32 => i32_suffixed
     i64 => i64_suffixed
+    i128 => i128_suffixed
     isize => isize_suffixed
 
     u8 => u8_suffixed
     u16 => u16_suffixed
     u32 => u32_suffixed
     u64 => u64_suffixed
+    u128 => u128_suffixed
     usize => usize_suffixed
 
     f32 => f32_suffixed
     f64 => f64_suffixed
 }
 
-#[cfg(integer128)]
-primitive! {
-    i128 => i128_suffixed
-    u128 => u128_suffixed
-}
-
 impl ToTokens for char {
     fn to_tokens(&self, tokens: &mut TokenStream) {
         tokens.append(Literal::character(*self));
diff --git a/tests/conditional/integer128.rs b/tests/conditional/integer128.rs
deleted file mode 100644
index 61e2274..0000000
--- a/tests/conditional/integer128.rs
+++ /dev/null
@@ -1,11 +0,0 @@
-#[test]
-fn test_integer128() {
-    let ii128 = -1i128;
-    let uu128 = 1u128;
-
-    let tokens = quote! {
-        #ii128 #uu128
-    };
-    let expected = "-1i128 1u128";
-    assert_eq!(expected, tokens.to_string());
-}
diff --git a/tests/test.rs b/tests/test.rs
index d41079e..1ddd153 100644
--- a/tests/test.rs
+++ b/tests/test.rs
@@ -9,11 +9,6 @@
 use proc_macro2::{Ident, Span, TokenStream};
 use quote::TokenStreamExt;
 
-mod conditional {
-    #[cfg(integer128)]
-    mod integer128;
-}
-
 struct X;
 
 impl quote::ToTokens for X {
@@ -125,18 +120,20 @@
     let ii16 = -1i16;
     let ii32 = -1i32;
     let ii64 = -1i64;
+    let ii128 = -1i128;
     let iisize = -1isize;
     let uu8 = 1u8;
     let uu16 = 1u16;
     let uu32 = 1u32;
     let uu64 = 1u64;
+    let uu128 = 1u128;
     let uusize = 1usize;
 
     let tokens = quote! {
-        #ii8 #ii16 #ii32 #ii64 #iisize
-        #uu8 #uu16 #uu32 #uu64 #uusize
+        #ii8 #ii16 #ii32 #ii64 #ii128 #iisize
+        #uu8 #uu16 #uu32 #uu64 #uu128 #uusize
     };
-    let expected = "-1i8 -1i16 -1i32 -1i64 -1isize 1u8 1u16 1u32 1u64 1usize";
+    let expected = "-1i8 -1i16 -1i32 -1i64 -1i128 -1isize 1u8 1u16 1u32 1u64 1u128 1usize";
     assert_eq!(expected, tokens.to_string());
 }