To get metapad built within Dev-C++, take the Makefile that 
is generated and add the following to the top:

    RICHEDIT = USE_RICH_EDIT
    #RICHEDIT = NO_RICH_EDIT

Then edit the lines corresponding to those below:

    WINDRES = windres.exe --define $(RICHEDIT)
    CC   = gcc.exe --define $(RICHEDIT)

This will ensure that config flags are passed properly. Lastly, 
tell Dev-C++ to use your custom Makefile so it doesn't overwrite 
the changes.