Apply clang-format universally.

* It is tough to contribute to a project that doesn't use a formatter,
* It is extra hard to contribute to a project which has configured the formatter, but ignores it for some files
* Code formatting makes it harder to hide obscure / weird bugs by accident or on purpose,

Let's rip the bandaid off?

Note that PRs currently in flight should be able to be merged relatively easily by applying `clang-format` to their tip prior to merge.

src/libexpr-c/nix_api_external.cc

@@ -48,11 +48,13 @@ class NixCExternalValue : public nix::ExternalValueBase
 public:
     NixCExternalValue(NixCExternalValueDesc & desc, void * v)
         : desc(desc)
-        , v(v){};
+        , v(v) {};
+
     void * get_ptr()
     {
         return v;
     }
+
     /**
      * Print out the value
      */
@@ -155,11 +157,17 @@ public:
         }
         nix_string_context ctx{context};
         desc.printValueAsXML(
-            v, (EvalState *) &state, strict, location, &doc, &ctx, &drvsSeen,
+            v,
+            (EvalState *) &state,
+            strict,
+            location,
+            &doc,
+            &ctx,
+            &drvsSeen,
             *reinterpret_cast<const uint32_t *>(&pos));
     }
 
-    virtual ~NixCExternalValue() override{};
+    virtual ~NixCExternalValue() override {};
 };
 
 ExternalValue * nix_create_external_value(nix_c_context * context, NixCExternalValueDesc * desc, void * v)