Add new rotbuf primitives
Rewrite keyring pack/unpack for extensibility

Use new rotbuf primitives to handle rotated buffers
Improve test framework: set TFWSOURCE env var
Add keyring back-compatibility test case
Add keyring test case (combined PINs)
Improve keyring pack code
Fix keyring test copyright and header comments
Add erealloc() function to mem.h, mem.c
Add alloca_str_toprint_quoted() macro to str.h
Fix rotbuf_advance(), add rotbuf_remain()
Add "keyring dump" command
Use "keyring dump" command in back-compatible keyring test
Merge branch 'new-keyring' into 'development'