allow filter size to be greater than feature map size in SAME convolution
allow filter size to be greater than feature map size in SAME convolution


Former-commit-id: 4a56accd9d28e96f461ee0154915571ea5215949
chunyang-wen/dynet,danielhers/dynet,shuheik/dynet,clab/cnn,xunzhang/dynet,shuheik/dynet,clab/dynet,clab/dynet,shuheik/dynet,xunzhang/dynet,chunyang-wen/dynet,danielhers/dynet,shuheik/dynet,danielhers/dynet,clab/dynet,clab/cnn,danielhers/dynet,shuheik/dynet,clab/cnn,xunzhang/dynet,shuheik/dynet,danielhers/dynet,danielhers/dynet,clab/dynet,clab/dynet,clab/dynet,chunyang-wen/dynet,clab/dynet,chunyang-wen/dynet,danielhers/dynet,shuheik/dynet,xunzhang/dynet