only use PUBLIC in PDAL_LINKAGE if CMake supports it, otherwise stick with LINK_PUBLIC
Exclude PCLBlockFilterTest when building w/o PCL

This patch puts filters/PCLBlockFilterTest.cpp inside a WITH_PCL check,
so we build with it only when we have PCL available.
Make stage's m_schema protected.
Fix small comment typo
Merge pull request #284 from gadomski/typo-fixes

Fix small comment typo
Merge branch 'master' into issues/264-pdal-linkage
tweak 'pdal delta' output a little, clean up docs
Add binary byte-ordering streams.
add an example LAS file with one missing point and incorrect header count
Merge pull request #285 from abellgithub/schema-ref

Make stage's m_schema protected.
Merge pull request #286 from abellgithub/iostream

Add binary byte-ordering streams.
Add BPF files.
some more cleanups related to #285
Merge pull request #275 from gadomski/exclude-pcl-test-cpp

Exclude PCLBlockFilterTest when building w/o PCL
use boost-latest ppa's to upgrade travis config
upgrade Vagrant to use boost 1.55 too
Merge pull request #287 from abellgithub/bpf

Add BPF files.
Very simple decompression for BPF.
Add a sbet reader

Sbet is a simple binary format used to store inertial measurement unit
(IMU) data. These data include position and trajectory information.
Simplify some code in dimension.
Make things fit in 80 columns.