Prepare branch for 3.12.0.0 release

- Updated version string
- Updated CHANGELOG

Author: mbr0wn

CHANGELOG

@@ -6,19 +6,19 @@ Change Log for Releases
         includes fan, fix issue with 1GigE, switch to 2 radio blocks
         with 2 channels each, upgrade TDC to version 2.0
 * X300: Enable BasicRX to use A/B/AB/BA muxing setups, more consistent
-        logging
+        logging, fix enumeration issue with TwinRX
 * USRP2/N2x0: Re-add ability to modulate in the DAC, improve ISE
               settings to better meet timing
 * B205mini: Fix global reset, improve timing in b205_ref_pll
 * UHD: Remove a lot of Boost usage, mostly replaced by C++11 features,
        more unit tests, fix Boost 1.67 compatibility, fix compiler
-       warnings, add API to query clock rate range,
+       warnings, add API to query clock rate range, fix get_usrp_?x_info
 * MPM: Refactored N3xx code, moved C++ standard to 14, refactor
        Boost.Python bindings, use CMake variable MPM_DEVICE
 * Logging: Allow disabling fastpath msgs at runtime
 * Docs: Clarified meaning of DSP frequencies, improved manual
         section on synchronization, added some known issues to B100,
-        USRP2, and USRP1
+        USRP2, and USRP1, update test test procedure description
 * Examples: Improved benchmark_rate (added failure thresholds, fixed
   incorrect calculation of samples on drops, fixed timeout values),
   minor fixes to txrx_loopback_to_file
@@ -27,6 +27,7 @@ Change Log for Releases
 * RFNoC: DDCs/DUCs use DDSes instead of CORDIC, add DMA-based replay
          block in FPGA, add 64-bit support to axi_wrapper, add compat
          number to radio block,
+* Debian: Fix rules file, fix Changelog format
 * Fix license headers
 * This release includes all bugfixes and features from previous
   releases, in particular, the 3.11.* release cycle

host/cmake/Modules/UHDVersion.cmake

@@ -20,8 +20,8 @@ FIND_PACKAGE(Git QUIET)
 SET(UHD_VERSION_MAJOR   3)
 SET(UHD_VERSION_API    12)
 SET(UHD_VERSION_ABI     0)
-SET(UHD_VERSION_PATCH git)
-SET(UHD_VERSION_DEVEL TRUE)
+SET(UHD_VERSION_PATCH   0)
+SET(UHD_VERSION_DEVEL FALSE)
 
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 # If we're on a development branch, we skip the patch version