Use built-in __APPLE__ macro instead of SYS_DARWIN and MACOSX

git-svn-id: file:///data/workdir/Transmission-svn//trunk@14310 1bcf1a7e-6170-4b50-b784-84ec52b2dec6
(trunk, libT) #5709 'Fix an instance of time_t printing' -- fixed, patch by naddy

git-svn-id: file:///data/workdir/Transmission-svn//trunk@14311 1bcf1a7e-6170-4b50-b784-84ec52b2dec6
(trunk, libT) #5699 'Toggle Inspector's Origin: is incorrect' -- fixed, patch by enzotrew

git-svn-id: file:///data/workdir/Transmission-svn//trunk@14312 1bcf1a7e-6170-4b50-b784-84ec52b2dec6
group upload and download size is too big on 10.9

git-svn-id: file:///data/workdir/Transmission-svn//trunk@14313 1bcf1a7e-6170-4b50-b784-84ec52b2dec6