The Microchip MPLAB C30 cross-compiler does not come with the C99 standard header <stdbool.h>. The dsPIC Helper Library provides the boolean.h to take its place. It defines the type bool and the true and false manifest constants.
To use these types, you can use the -I compiler option to add the dsPIC Helper Library source directory to the compiler command line, and then include the header file like so:
#include <boolean.h>