This old workaround is not necessary and could not be used anyhow since
it would affect a way too wide range of drivers. Modern drivers should
be able to honor the default GL_UNPACK_ALIGNMENT of 4 even for 1 byte
per pixel formats like GL_ALPHA. Instead, document why the behavior
is correct.

Change-Id: I1687448ba92875c8ff772ccc371894e88ff64096
Reviewed-by: Gunnar Sletta <gunnar.sletta@jollamobile.com>