Rename debugging_opts to unstable_opts

This is no longer used only for debugging options (e.g. `-Zoutput-width`, `-Zallow-features`).
Rename it to be more clear.

Author: jyn514

src/allocator.rs

@@ -24,7 +24,7 @@ pub(crate) fn codegen(
             unwind_context,
             kind,
             tcx.lang_items().oom().is_some(),
-            tcx.sess.opts.debugging_opts.oom,
+            tcx.sess.opts.unstable_opts.oom,
         );
         true
     } else {

src/cast.rs

@@ -144,7 +144,7 @@ pub(crate) fn clif_int_or_float_cast(
             fx.bcx.ins().fcvt_to_uint_sat(to_ty, from)
         };
 
-        if let Some(false) = fx.tcx.sess.opts.debugging_opts.saturating_float_casts {
+        if let Some(false) = fx.tcx.sess.opts.unstable_opts.saturating_float_casts {
             return val;
         }
 

src/debuginfo/line_info.rs

@@ -140,7 +140,7 @@ impl<'tcx> DebugContext<'tcx> {
             // In order to have a good line stepping behavior in debugger, we overwrite debug
             // locations of macro expansions with that of the outermost expansion site
             // (unless the crate is being compiled with `-Z debug-macros`).
-            let span = if !span.from_expansion() || tcx.sess.opts.debugging_opts.debug_macros {
+            let span = if !span.from_expansion() || tcx.sess.opts.unstable_opts.debug_macros {
                 span
             } else {
                 // Walk up the macro expansion chain until we reach a non-expanded span.

src/driver/aot.rs

@@ -33,7 +33,7 @@ fn make_module(sess: &Session, isa: Box<dyn TargetIsa>, name: String) -> ObjectM
     // Unlike cg_llvm, cg_clif defaults to disabling -Zfunction-sections. For cg_llvm binary size
     // is important, while cg_clif cares more about compilation times. Enabling -Zfunction-sections
     // can easily double the amount of time necessary to perform linking.
-    builder.per_function_section(sess.opts.debugging_opts.function_sections.unwrap_or(false));
+    builder.per_function_section(sess.opts.unstable_opts.function_sections.unwrap_or(false));
     ObjectModule::new(builder)
 }
 

src/intrinsics/mod.rs

@@ -676,7 +676,7 @@ fn codegen_regular_intrinsic_call<'tcx>(
                 && !layout.might_permit_raw_init(
                     fx,
                     InitKind::Zero,
-                    fx.tcx.sess.opts.debugging_opts.strict_init_checks) {
+                    fx.tcx.sess.opts.unstable_opts.strict_init_checks) {
 
                 with_no_trimmed_paths!({
                     crate::base::codegen_panic(
@@ -692,7 +692,7 @@ fn codegen_regular_intrinsic_call<'tcx>(
                 && !layout.might_permit_raw_init(
                     fx,
                     InitKind::Uninit,
-                    fx.tcx.sess.opts.debugging_opts.strict_init_checks) {
+                    fx.tcx.sess.opts.unstable_opts.strict_init_checks) {
 
                 with_no_trimmed_paths!({
                     crate::base::codegen_panic(