x300_dboard_iface: added UHD_UNUSED() macro to unused parameters in set_clock_enabled()

* Removes GCC warning about unused parameters
Merge branch 'maint'
Added missing pure virtual destructors to base classes
Updated ABI version string
Give user the option to ignore daughterboard's calibration file at runtime

* Add "ignore-cal-file" to the uhd::device_addr_t arguments
* Added documentation for new feature
ad9361: Made recommended rate a constant
b200: Set sensible defaults for freq, gain and rate at startup
cbx: Fixed LO FRAC truncation
usrp: don't print duplicate GPSDO detection messages
uhd_dump: use LIBS instead of LDFLAGS

This allows distro override for LDFLAGS and doesn't break the build process.

Signed-off-by: Jaroslav Škarvada <jskarvad@redhat.com>
chdr-dissector: fix wireshark-1.12 detection

Signed-off-by: Jaroslav Škarvada <jskarvad@redhat.com>
uhd: Added an operator/ for (fs_path, size_t)

This is useful when constructing property tree paths.
With this path, the following code would be valid:

size_t mb_index = 0;
fs_path mb_root = "/mboards";
mb_root = mb_root / mb_index;

This is a shortcut for the (in UHD very common)

mb_root = mb_root / boost::lexical_cast<std::string(mb_index);
Merge branch 'maint'
sbx: Fixed logging string (showed TX instead of RX)
uhd: Fixed logging bug (#476) -- UHD logging has unexplained effect on packet loss.
- Removed logging from radio_ctrl_core_3000
- Changed logging facility to prevent type conversion when message is not logged
x300: Added output sync for DAC reference clocks
Merge branch 'maint'
fpga: Multiple X300 FPGA bugfixes and enhancements

- Fixed 10GigE firmware communication issues and sequence errors for TX
- Multiple changes to help ease timing closure
- Cleaned up build scripts
- Switched to Xilinx ISE 14.7 as the default build tool for X300
docs: Changed Xilinx ISE version from 14.4 to 14.7
Updated ChangeLog for 3.7.2