Move validation checks into new function rhizome_manifest_validate()
Remove rhizome_manifest 'errors' field
Replace rhizome_manifest 'warnings' with 'malformed'
Replace rhizome_manifest 'manifest_bytes' with 'manifest_body_bytes' and
refactor to use 'manifest_all_bytes' in all manifest i/o
Refactor rhizome_manifest_verify() and reverse sense of return value to
match rhizome_manifest_validate()
New function rhizome_manifest_inspect() -- lightweight manifest parser
used when receiving Rhizome advertisements
New 'rhizomeops' test case for invalid manifest "service" field values,
now passes
All ob_append_xxx(b,...) functions return void
ob_makespace() returns 1 if successful, 0 if not
Add ob_overrun(b) predicate to check for overrun after any number of
appends
