slicetype: fix bcost behavior with signed ints

--HG--
branch : stable
nits

--HG--
branch : stable
reference: pad width of weighted region to multiple of 16

--HG--
branch : stable
fix b-pyramid for fixed GOP

--HG--
branch : stable
slicetype: prevent compiler warnings about uninitialized variables

--HG--
branch : stable
y4m: prevent infinite loop on malformed y4m frame headers

--HG--
branch : stable
input: use ifstream::good() instead of !ifstream::fail()

good() implies bad, fail, and eof flags are all false. The fail() flag does
not include eof status or the bad bit for I/O errors.

--HG--
branch : stable
yuv: support colorspaces in YUV input files (closes #13)

--HG--
branch : stable
input: add build flag to disable read thread for debug purposes

--HG--
branch : stable