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/ARMAssembler.h b/libpixelflinger/codeflinger/ARMAssembler.h
index 7178c65..76acf7e 100644
--- a/libpixelflinger/codeflinger/ARMAssembler.h
+++ b/libpixelflinger/codeflinger/ARMAssembler.h
@@ -35,7 +35,7 @@
 class ARMAssembler : public ARMAssemblerInterface
 {
 public:
-                ARMAssembler(const sp<Assembly>& assembly);
+    explicit    ARMAssembler(const sp<Assembly>& assembly);
     virtual     ~ARMAssembler();
 
     uint32_t*   base() const;