OK. To answer your question there is one other exe file in C:\Program Files\CodeBlocks\MinGW\gdb32\bin. That is gdbserver32.exe
Removing Python 3.5 has fixed the problem.
A possibly related issue I had was with as.exe. I develop my C code using the CodeBlocks IDE but compile for release using a DOS batch file. This batch process has to run on both my own PC and a server we use for release software.
Older versions of CodeBlocks did not need the PATH variable to be set. Instead I used the CODEBLOCKS environment variable and both the IDE and batch files worked.
With 17:12 the IDE worked but the batch file did not because as.exe could not find libintl-8.dll. This seemed to be because there are two copies of as.ex; one in C:\Program Files\CodeBlocks\MinGW\bin which also has the DLL, and one in C:\Program Files\CodeBlocks\MinGW\mingw32\bin which doesn't have the DLL.as
This is fixed by adding c:\program files\codeblocks\mingw\bin to PATH. Using the CODEBLOCKS variable was slightly easier because it could be set on the fly in the batch file.
Once again thanks for you help,
Malcolm