Do not disable InnoDB inlining when UNIV_DEBUG is defined. The
inlining is now solely controlled by the preprocessor symbol
UNIV_MUST_NOT_INLINE and by any compiler options.

mtr_memo_contains(): Add an explicit type conversion from void*, so
that the function can be compiled by a C++ compiler. Previously, this
function was never seen by the C++ compiler, because it is only
present in UNIV_DEBUG builds and InnoDB inlining used to be disabled.

buf_flush_validate_skip(): A wrapper that skips most calls of
buf_flush_validate_low(). Invoked by debug assertions in
buf_flush_insert_into_flush_list() and buf_flush_remove().

fil_validate_skip(): A wrapper that skips most calls of
fil_validate(). Invoked by debug assertions in fil_io() and fil_io_wait().

os_aio_validate_skip(): A wrapper that skips most calls of
os_aio_validate(). Invoked by debug assertions in
os_aio_func(), os_aio_windows_handle() and os_aio_simulated_handle.

os_get_os_version(): Only include this function if __WIN__ is defined.

sync_array_deadlock_step(): Slight optimizations. This function is a
major CPU consumer in UNIV_SYNC_DEBUG builds.