Renamed most C files to C++: *.c to *.cc

Also:
 - Fixed C++ related compilation errors.
 - Added missing 'extern "C"' guards in some of the header files.
 - Added missing LOCAL_CPP_EXTENSION to Android.mk files.
 - Added-back btif/src/btif_mce.cc and bta/mce/bta_mce_* to
   btif/Android.mk and bta/Android.mk respectively.
 - Fixed the alphabetical ordering of the *.cc files in some
   of the Android.mk files.
 - Added missing Copyright header to "osi/include/list.h"
 - Updated "osi/src/wakelock.cc" to use C++ std::string
   instead of dynamic allocation of C-style strings.

Test: code compilation, unit tests, and A2DP streaming
Change-Id: Ia2f7215ed9df32775c701b68fc86b09875b942c7