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/ARMAssemblerProxy.h b/libpixelflinger/codeflinger/ARMAssemblerProxy.h
index b852794..10d0390 100644
--- a/libpixelflinger/codeflinger/ARMAssemblerProxy.h
+++ b/libpixelflinger/codeflinger/ARMAssemblerProxy.h
@@ -34,7 +34,7 @@
     // ARMAssemblerProxy take ownership of the target
 
                 ARMAssemblerProxy();
-                ARMAssemblerProxy(ARMAssemblerInterface* target);
+    explicit    ARMAssemblerProxy(ARMAssemblerInterface* target);
     virtual     ~ARMAssemblerProxy();
 
     void setTarget(ARMAssemblerInterface* target);