added missing bson-json.h to install list
Merge pull request #31 from guruofquality/fix_missing_include

added missing bson-json.h to install list
Added missing librt to cmake which is required by clock_gettime.

librt does not automatically link for Ubuntu 12.04 for example,
so I added some changed to explicily link against it when found.
The changes to the CMakeLists.txt should be cross platform safe
since the changes are all conditionalized with if (RT_LIBRARY)
build: properly check for clang >= 3.3
Merge pull request #32 from guruofquality/fix_missing_librt

Added missing librt to cmake which is required by clock_gettime.
add config/install libbson-1.0.pc to cmake build
Merge pull request #33 from guruofquality/added_pkgconfig

add config/install libbson-1.0.pc to cmake build
build: fix underterminated preprocessor statement.
move BSON_OS_* to bson-macros.h.
windows: GetTickCount64 is in milliseconds.
clock: ugh, bump win32 monotonic clock again.
win32: fix some win32 warnings.
win32: disable warning for benign redefinition of type.
win32: various _MSC_VER warning fixups.
B-0 merged from 10Gen branch after rebase