Convert DF_SCAN etc from #define to an enum
Whilst debugging an issue in df, I noticed that there are
some #define constants that could be an enum (thus making them known
to gdb).
Convert them to a new enum, and update the "id" field of
struct df_problem.
gcc/ChangeLog:
* df.h (DF_SCAN, DF_LR, DF_LIVE, DF_RD, DF_CHAIN, DF_WORD_LR,
DF_NOTE, DF_MD, DF_MIR, DF_LAST_PROBLEM_PLUS1): Convert from
#define to...
(enum df_problem_id): ...this new enum.
(struct df_problem): Convert field "id" from "int" to
enum df_problem_id.
From-SVN: r235522