Fix warnings in libutils headers

system/core/include is included in the global include path using
-isystem, which hides all warnings.  Fix warnings in libutils
headers in preparation for moving from -isystem to -I.

- Fix implicit cast from int64_t to long in Condition.h.  Remove
  the __LP64__ check and always compare against LONG_MAX before
  casting.
- Fix implicit cast from size_t to ssize_t in KeyedVector.h
- Fix -Wshadow-field-in-constructor warnings in Looper.h and RefBase.h
- Move destructors for MessageHandler and LooperCallback to Looper.cpp
  and ReferenceRenamer and VirtualLightRefBase to RefBase.cpp to prevent
  vtables in every compilation unit.
- Declare template variables in Singleton.h
- Fix old-style casts in StrongPointer.h and TypeHelpers.h
- Use template metaprogramming in TypeHelpers.h to avoid warnings on
  memmove on non-trivial types.
- Add an assignment operator to key_value_pair_t to complete
  rule-of-three
- Use memcpy instead of dereferencing a reinterpret_casted pointer to
  treat the bits of a float or double as int32_t or int64_t
- Escape unicode sequences inside doxygen comments between \code and
  \endcode
- Remove WIN32 ZD definition in Compat.h, %zd works fine with mingw
- Fix WIN32 printf warnings in Filemap.cpp
- Initialize mNullValue with 0 in LruCache.h, some of the tests use a
  non-pointer type for TValue.

Test: m -j native
Bug: 31492149
Change-Id: I385a05a3ca01258e44fe3b37ef77e4aaff547b26