adjust error messages for lower-case start

tests/compile-fail/overflowing-unchecked-rsh.rs

@@ -2,7 +2,7 @@
 
 use std::intrinsics::*;
 
-//error-pattern: Overflowing shift by 64 in `unchecked_shr`
+//error-pattern: overflowing shift by 64 in `unchecked_shr`
 
 fn main() {
     unsafe {

tests/compile-fail/unchecked_add1.rs

@@ -1,5 +1,5 @@
 #![feature(core_intrinsics)]
 fn main() {
     // MAX overflow
-    unsafe { std::intrinsics::unchecked_add(40000u16, 30000); } //~ ERROR Overflow executing `unchecked_add`
+    unsafe { std::intrinsics::unchecked_add(40000u16, 30000); } //~ ERROR overflow executing `unchecked_add`
 }

tests/compile-fail/unchecked_add2.rs

@@ -1,5 +1,5 @@
 #![feature(core_intrinsics)]
 fn main() {
     // MIN overflow
-    unsafe { std::intrinsics::unchecked_add(-30000i16, -8000); } //~ ERROR Overflow executing `unchecked_add`
+    unsafe { std::intrinsics::unchecked_add(-30000i16, -8000); } //~ ERROR overflow executing `unchecked_add`
 }

tests/compile-fail/unchecked_div1.rs

@@ -1,5 +1,5 @@
 #![feature(core_intrinsics)]
 fn main() {
     // MIN/-1 cannot be represented
-    unsafe { std::intrinsics::unchecked_div(i16::MIN, -1); } //~ ERROR Overflow executing `unchecked_div`
+    unsafe { std::intrinsics::unchecked_div(i16::MIN, -1); } //~ ERROR overflow executing `unchecked_div`
 }

tests/compile-fail/unchecked_mul1.rs

@@ -1,5 +1,5 @@
 #![feature(core_intrinsics)]
 fn main() {
     // MAX overflow
-    unsafe { std::intrinsics::unchecked_mul(300u16, 250u16); } //~ ERROR Overflow executing `unchecked_mul`
+    unsafe { std::intrinsics::unchecked_mul(300u16, 250u16); } //~ ERROR overflow executing `unchecked_mul`
 }

tests/compile-fail/unchecked_mul2.rs

@@ -1,5 +1,5 @@
 #![feature(core_intrinsics)]
 fn main() {
     // MIN overflow
-    unsafe { std::intrinsics::unchecked_mul(1_000_000_000i32, -4); } //~ ERROR Overflow executing `unchecked_mul`
+    unsafe { std::intrinsics::unchecked_mul(1_000_000_000i32, -4); } //~ ERROR overflow executing `unchecked_mul`
 }

tests/compile-fail/unchecked_sub1.rs

@@ -1,5 +1,5 @@
 #![feature(core_intrinsics)]
 fn main() {
     // MIN overflow
-    unsafe { std::intrinsics::unchecked_sub(14u32, 22); } //~ ERROR Overflow executing `unchecked_sub`
+    unsafe { std::intrinsics::unchecked_sub(14u32, 22); } //~ ERROR overflow executing `unchecked_sub`
 }

tests/compile-fail/unchecked_sub2.rs

@@ -1,5 +1,5 @@
 #![feature(core_intrinsics)]
 fn main() {
     // MAX overflow
-    unsafe { std::intrinsics::unchecked_sub(30000i16, -7000); } //~ ERROR Overflow executing `unchecked_sub`
+    unsafe { std::intrinsics::unchecked_sub(30000i16, -7000); } //~ ERROR overflow executing `unchecked_sub`
 }