vppinfra: minor tweaks for cgo interoperation

vppinfra: minor tweaks for cgo interoperation

'type' is a keyword in golang, so s/type/event_type/ in elog.h and
elsewhere.

Add vec_len_not_inline(...), elog_write_file_not_inline(...) and
elog_read_file_not_inline(...) since the inline forms aren't usable.

More such tweaks may follow.

Type: improvement
Signed-off-by: Dave Barach <dave@barachs.net>
Change-Id: I9a80a6afa635f5cdedee554ee9abe400fafc1cb6