Make some error messages lowercase

Author: Aaron1011

src/shims/backtrace.rs

@@ -77,7 +77,7 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
 
         let ptr = match this.read_scalar(ptr)?.check_init()? {
             Scalar::Ptr(ptr) => ptr,
-            Scalar::Raw { .. } => throw_ub_format!("Expected a pointer in `rust_miri_resolve_frame`, found {:?}", ptr)
+            Scalar::Raw { .. } => throw_ub_format!("expected a pointer in `rust_miri_resolve_frame`, found {:?}", ptr)
         };
 
         let fn_instance = if let Some(GlobalAlloc::Function(instance)) = this.tcx.get_global_alloc(ptr.alloc_id) {
@@ -87,7 +87,7 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
         };
 
         if dest.layout.layout.fields.count() != 4 {
-            throw_ub_format!("Bad declaration of miri_resolve_frame - should return a struct with 4 fields");
+            throw_ub_format!("bad declaration of miri_resolve_frame - should return a struct with 4 fields");
         }
 
         let pos = BytePos(ptr.offset.bytes().try_into().unwrap());

tests/compile-fail/backtrace/bad-backtrace-decl.rs

@@ -7,7 +7,7 @@ fn main() {
     let frames = unsafe { miri_get_backtrace(0) };
     for frame in frames.into_iter() {
         unsafe {
-            miri_resolve_frame(*frame, 0); //~ ERROR Undefined Behavior: Bad declaration of miri_resolve_frame - should return a struct with 4 fields
+            miri_resolve_frame(*frame, 0); //~ ERROR Undefined Behavior: bad declaration of miri_resolve_frame - should return a struct with 4 fields
         }
     }
 }

tests/compile-fail/backtrace/bad-backtrace-ptr.rs

@@ -4,6 +4,6 @@ extern "Rust" {
 
 fn main() {
     unsafe {
-        miri_resolve_frame(0 as *mut _, 0); //~ ERROR Undefined Behavior: Expected a pointer
+        miri_resolve_frame(0 as *mut _, 0); //~ ERROR Undefined Behavior: expected a pointer
     }
 }