Kernel change 62e32ac3505a0cab1c5ef8ea2c0eab3b26ed855f
renamed 'struct log' to 'struct printk_log'. Detect which kernel
version is being parsed and use the appropriate struct name.

Change-Id: I1a92623e8b4167f390d09051a52e6411ae3901ee

It can be useful to extract the dmesg from contexts other than the
--dmesg parser. Refactor the code into a top-level "library" module and
hook the --dmesg parser into that.

Change-Id: I935c05a081b1096d67343f5ce8617febb674b2e0