initial import - common build elements for c/c++
updated path to gitrev.pl
updated non-tagged executable suffix to always be 'unstable'
added DEFAULT_ETC_ALTERNATIVES_PRIORITY to VersionHelper

it is set to 0 when the executable version is -unstable, and 10
otherwise.
added FindSamtools.cmake
change build output dir to ${CMAKE_BINARY_DIR}/build to allow out-of-source builds
updated gitrev to support building from exported (non-git) repos
add default label "unit" to tests added with testhelper
add module to find "TRE" library
changed form of unstable version numbers

now, instead of just using the commit hash, if we generate a version for
a commit that is "past" a tag, we make something like:

v1.0.0-9-<commit hash>

to mean "we are 9 commits past v1.0.0".
add in modules for Cairo and Freetype
updated buildrev.pl to work in the absence of any tags
change single quotes to double
fix gitrev.pl when no tags are present (correctly this time)
added dpkg-deps script
make sure gitrev.pl marks unstable revisions as unstable
Merge branch 'master' of git://github.com/genome/build-common
update FindSamtools to look for /usr/include/bam.h
updated FindSamtools to work with Cent 6/EPEL pkg
Add new environment variable: BC_UNIT_TEST_VG

When set, unit tests will be run through valgrind