Fix host driver build failure due to missing includes

[devttys]

Host driver fails to compile on the latest master:

[ 10%] Building CXX object lib/CMakeFiles/uhd.dir/cal/database.cpp.o
In file included from /home/tyrell/Coding/antsdr_uhd/host/lib/cal/database.cpp:7:
/home/tyrell/Coding/antsdr_uhd/host/include/uhd/cal/database.hpp:86:24: error: ‘uint8_t’ was not declared in this scope
   86 |     static std::vector<uint8_t> read_cal_data(const std::string& key,
      |                        ^~~~~~~

[gettyhub]

The fix it says is to add cstdint to header files. Not a problem on Ubuntu but trouble for other builds. But then that's not the only errors encountered. More follow after that.