Minor optimization on image loading

Minor optimization on image loading

1. Wrap DALI_UNLIKELY if there was some system / file error.
e.g. fread, fseek faild. malloc faild. image size or format not valid.

2. Reduce Dali::Vector operation more times.
When we use fixed size of Dali::Vector, use void * or std::uint8_t*
instead of &vector[0]. It's for reducing function call of operator[]
so we don't check index range, so we don't call Dali::Vector::Count().

3. Don't setup initial value of buffer for some cases.
Note. gausian-blur.cpp defect will be fixed in Heeyong's stride patch.

4. Reduce useless operations on loader-ico.cpp
Previous code use 4 times memory + buffer overflow error exist
when bitcount is 1 + read mask buffer only for each line. not whole buffer.

Change-Id: I28cdd7468ec4d573e53f4f6f7ad2345bca60b273
Signed-off-by: Eunki, Hong <eunkiki.hong@samsung.com>