Adding GDB support to the makefile.  Use the build option DEBUG=GDB to have the .elf file contain debugging symbols.
MERGE - Adding GDB support to the makefile.  Use the build option
 DEBUG=GDB to have the .elf file contain debugging symbols.

git-svn-id: https://afrodevices.googlecode.com/svn/trunk/baseflight@303 7c89a4a9-59b9-e629-4cfe-3a2d53b20e61