Fix compiler warnings due to: a mismatch in the prototypes for
check_access and implicit conversions from double to ulonglong
and vice-versa.

mysys/my_getopt.c:
  Explicit conversion from ulonglong to double. Might need to
  be tweaked in the future.
sql/sql_parse.h:
  Make prototype equal to the case when not compiling under embedded.
sql/sys_vars.cc:
  Explicit conversion from ulonglong to double. Destination var
  is a ulonglong.
sql/sys_vars.h:
  Explicit conversion from ulonglong to double. Might need to
  be tweaked in the future.