Does not build: wrong argument in memcall.Protect: memcall.NoAccess... are functions

[pzeinlinger]

Describe the bug
A fresh go get of memguard results in vet errors.

github.com/awnumar/memguard/core

src/github.com/awnumar/memguard/core/buffer.go:84:29: cannot use memcall.NoAccess (type func() memcall.MemoryProtectionFlag) as type memcall.MemoryProtectionFlag in argument to memcall.Protect
src/github.com/awnumar/memguard/core/buffer.go:87:29: cannot use memcall.NoAccess (type func() memcall.MemoryProtectionFlag) as type memcall.MemoryProtectionFlag in argument to memcall.Protect
src/github.com/awnumar/memguard/core/buffer.go:121:30: cannot use memcall.ReadOnly (type func() memcall.MemoryProtectionFlag) as type memcall.MemoryProtectionFlag in argument to memcall.Protect
src/github.com/awnumar/memguard/core/buffer.go:142:30: cannot use memcall.ReadWrite (type func() memcall.MemoryProtectionFlag) as type memcall.MemoryProtectionFlag in argument to memcall.Protect
src/github.com/awnumar/memguard/core/buffer.go:165:29: cannot use memcall.ReadWrite (type func() memcall.MemoryProtectionFlag) as type memcall.MemoryProtectionFlag in argument to memcall.Protect
src/github.com/awnumar/memguard/core/exit.go:67:21: cannot use memcall.ReadWrite (type func() memcall.MemoryProtectionFlag) as type memcall.MemoryProtectionFlag in argument to memcall.Protect

To Reproduce
Steps to reproduce the behaviour:
go get github.com/awnumar/memguard