vendor: Update covertool for go1.10

[jodh-intel]

Re-vendor covertool to work with golang 1.10.

Changes:

5072b09 CI: Update travis for go1.10
7cf24e2 cover: Fix build for 1.10
d45792f command; Factor out a WriteProfilesToFile function
012b32c profile: Factor out WriteProfiles to its own file
a61bda3 merge: Rename WriteProfile to WriteProfiles for consitency
449c650 merge: Remove unused type
77573e5 merge: Remove spurious 'profile' in help text
e0e4815 travis: Add go 1.9 to the test matrix
df49b48 README: Add a new covertool section and more context for instrumented binaries
a89ec05 examples: Fix an "instrumented" typo

Fixes #1072.

Signed-off-by: James O. D. Hunt james.o.hunt@intel.com

[sboeuf]

LGTM

[devimc]

lgtm