Cygwin: simplify some function names

Cygwin: simplify some function names

Remove "32" or "64" from each of the following names: acl32,
aclcheck32, aclfrommode32, aclfrompbits32, aclfromtext32, aclsort32,
acltomode32, acltopbits32, acltotext32, facl32, fchown32, fcntl64,
fstat64, _fstat64, _fstat64_r, ftruncate64, getgid32, getgrent32,
getgrgid32, getgrnam32, getgroups32, getpwuid32, getpwuid_r32,
getuid32, getuid32, initgroups32, lseek64, lstat64, mknod32, mmap64,
setegid32, seteuid32, setgid32, setgroups32, setregid32, setreuid32,
setuid32, stat64, _stat64_r, truncate64.

Remove prototypes and macro definitions of these names.

Remove "#ifndef __INSIDE_CYGWIN__" from some headers so that the new
names will be available when compiling Cygwin.

Remove aliases that are no longer needed.

Include <unistd.h> in fhandler_clipboard.cc for the declarations of
geteuid and getegid.