This commit updates isc_result_t to be an enum type, thus allowing
debugging sessions to promptly identify the string used to define the
error number, e.g. ISC_R_NOMEMORY, instead of a number like 37.
It does so by having error codes defined in template files located in
lib/<libname>/result_<lib>.h.in, those files are combined during the
build stage to generate the enum type, stored in
lib/isc/include/isc/result_ext.h source file.
Diego Fronza
dc300d3e48