Merge 2.4 into master

Merged pull requests:
        #890 from caorong:patch-1 
        #893 from jet47:gpu-arm-fixes
        #933 from pengx17:2.4_macfix_cont
        #935 from pengx17:2.4_filter2d_fix
        #936 from bitwangyaoyao:2.4_perf
        #937 from bitwangyaoyao:2.4_fixPyrLK
        #938 from pengx17:2.4_surf_sample
        #939 from pengx17:2.4_getDevice
        #940 from SpecLad:autolock
        #941 from apavlenko:signed_char
        #946 from bitwangyaoyao:2.4_samples2
        #947 from jet47:fix-gpu-arm-build
        #948 from jet47:cuda-5.5-support
        #952 from SpecLad:jepg
        #953 from jet47:fix-bug-3069
        #955 from SpecLad:symlink
        #957 from pengx17:2.4_fix_corner_detector
        #959 from SpecLad:qt4-build
        #960 from SpecLad:extra-modules