hdf5: first stab at hdf5-1.10 support

This CL is a first step towards supporting new features and APIs
of HDF5 v1.10.

Right now, anecdotal evidence shows that HDF5 v1.8 is still massively
deployed so support for 1.10 has to be opt-in, by way of an optional
build tag aptly named "hdf5_v1.10"

Updates gonum#16.

.travis.yml

@@ -22,6 +22,9 @@ addons:
 env:
   global:
     - GODEBUG=cgocheck=0
+    - TAGS="hdf5_v1.8"
+    ## FIXME: add hdf5_v1.10 when trusty->bionic
+    ## - TAGS="hdf5_v1.8 hdf5_v1.10"
 
 notifications:
   email:
@@ -31,7 +34,7 @@ notifications:
     on_failure: always
 
 script:
- - go get -d -t -v ./...
- - go install -v ./...
- - go test -v ./...
+ - go get -d -t -v -tags="$TAGS" ./...
+ - go install -v -tags="$TAGS" ./...
+ - go test -v -tags="$TAGS" ./...
 

README.md

@@ -15,11 +15,15 @@ Naive ``cgo`` bindings for the ``C-API`` of ``hdf5``.
 
 - Writing/reading an ``hdf5`` with compound data: [cmd/test-go-cpxcmpd/main.go](https://github.com/gonum/hdf5/blob/master/cmd/test-go-cpxcmpd/main.go)
 
-## Note
+## Notes
 
 - *Only* version *1.8.x* of ``HDF5`` is supported.
 - In order to use ``HDF5`` functions in more than one goroutine simultaneously, you must build the HDF5 library with threading support. Many binary distributions (RHEL/centos/Fedora packages, etc.) do not have this enabled. Therefore, you must build HDF5 yourself on these systems.
-
+- By default, `gonum/hdf5` is assuming to be compiled against `hdf5-v1.8.x`.
+  If you want to take advantage of the new features of `hdf5-v1.10.x`, please build it with the `hdf5_v1.10` build tag:
+	```
+	$> go install -tags="hdf5_v1.10" ./...
+	```
 
 ## Known problems
 

h5f_v1.10.go

@@ -0,0 +1,15 @@
+// Copyright ©2018 The gonum Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//+build hdf5_v1.10
+
+package hdf5
+
+// #include "hdf5.h"
+import "C"
+
+// StartSWMRWrite enables SWMR writing mode for this file.
+func (f *File) StartSWMRWrite() error {
+	return h5err(C.H5Fstart_swmr_write(f.id))
+}