Fix google-explicit-constructor warnings in system/core.

* Declare explicit conversion constructors.
* Add NOLINT for implicit conversion constructors.
* Fix also some misaligned indendations.

Bug: 28341362
Change-Id: Idf911f35923b408d92285cc1a053f382ba08c63e
Test: build with clang-tidy
diff --git a/libpixelflinger/codeflinger/CodeCache.h b/libpixelflinger/codeflinger/CodeCache.h
index 0fb6fd5..c0e0684 100644
--- a/libpixelflinger/codeflinger/CodeCache.h
+++ b/libpixelflinger/codeflinger/CodeCache.h
@@ -42,7 +42,7 @@
 class AssemblyKey : public AssemblyKeyBase
 {
 public:
-    AssemblyKey(const T& rhs) : mKey(rhs) { }
+    explicit AssemblyKey(const T& rhs) : mKey(rhs) { }
     virtual int compare_type(const AssemblyKeyBase& key) const {
         const T& rhs = static_cast<const AssemblyKey&>(key).mKey;
         return android::compare_type(mKey, rhs);
@@ -56,7 +56,7 @@
 class Assembly
 {
 public:
-                Assembly(size_t size);
+    explicit    Assembly(size_t size);
     virtual     ~Assembly();
 
     ssize_t     size() const;
@@ -80,13 +80,13 @@
 {
 public:
 // pretty simple cache API...
-                CodeCache(size_t size);
-                ~CodeCache();
-    
-            sp<Assembly>        lookup(const AssemblyKeyBase& key) const;
+    explicit            CodeCache(size_t size);
+                        ~CodeCache();
 
-            int                 cache(  const AssemblyKeyBase& key,
-                                        const sp<Assembly>& assembly);
+    sp<Assembly>        lookup(const AssemblyKeyBase& key) const;
+
+    int                 cache(const AssemblyKeyBase& key,
+                              const sp<Assembly>& assembly);
 
 private:
     // nothing to see here...
@@ -105,7 +105,7 @@
         const AssemblyKeyBase* mKey;
     public:
         key_t() { };
-        key_t(const AssemblyKeyBase& k) : mKey(&k)  { }
+        explicit key_t(const AssemblyKeyBase& k) : mKey(&k)  { }
     };
 
     mutable pthread_mutex_t             mLock;