* some further optimizations and cleanups in dnn:
+ got rid of dnn::gemm; it's not perf critical anymore (perhaps)
+ embedded col2im functionality into convolution_layer.cpp, since it's not used anywhere else
+ parallel max pooling. even better performance can be achieved if we knew that max indices are not needed (and they are not needed in most networks)
+ somewhat optimized deconvolution layer: optimized bias addition (merged it with col2im), optimized col2im slightly.
+ hopefully fixed incorrect memory access in fully-connected layer; restored aligned memory reads (they should work fine now)

* hopefully fixed regressions in ENet performance

* fixed some typos in deconvolution; added SIMD optimization for the max pooling layer

* fixed warnings in SIMD-less build configuration