bionic: eliminate __RENAME_CLANG in favor of __RENAME

Checks on __clang__ have been removed from bionic, making the
__RENAME_CLANG macro unnecessary. Switch all __RENAME_CLANG instances
back to __RENAME. Restore send.cpp and cdefs.h to an unmodified state.

Bug: 113293072
Change-Id: I262ee167e1b89b908546cd835189c71d84b5fdf7