dump/restore: define variables in exactly one compilation unit

[mckusick]

Summary

This fixes the build of the dump and restore utilities with -fno-common. Redundant initialization in itime.c have been removed.

The changes formerly in D24209 (primarily the change in <protocols/dumprestore.h>) have been merged into this change so that all the fixes to enable -fno-common for dump and restore are in one place.

Test Plan

Verify that dump | restore still works as previously.

[mckusick]

I prefer just using extern and then declaring the actual variables in the function in which they are most prominent, but using EXTERN as you have done does work fine.

[mckusick]

Rather than doing EXTERN, move the explicit declarations into file as this:
mapsize - main.c
usedinomap - main.c
dumpdirmap - main.c
dumpinomap - main.c
disk - main.c
tape - main.c
popenout - main.c
dumpdates - itime.c
temp - unused, remove from dump.h, main.c, and definition of _PATH_DTMP from pathnames.h
lastlevel - itime.c
level - main.c
uflag - main.c
diskfd - main.c
tapefd - tape.c
pipeout - main.c
curino - tape.c
newtape - tape.c
density - already declared in main.c
tapesize - main.c
tsize - main.c
asize - tape.c
etapes - main.c
nonodump - main.c
unlimited - main.c
cachesize - already declared in main.c
rsync_friendly - main.c
notify - already declared in main.c
blockswritten - already declared in main.c
tapeno - already declared in main.c
tstart_writing - main.c
tend_writing - main.c
passno - main.c
sblock - main.c
dev_bsize - already declared in main.c
dev_bshift - main.c
tp_bshift - main.c
dumpdates - leave in itime.c
nddates - leave in itime.c
If you would like me to take over this project, I am willing to do so.

[mckusick]

Taking over with Kyle Evans blessing.

[mckusick]

Rather than using EXTERN, place each global declaration into the file in which it is primarily used.

[kevans]

Looks good and compiles with -fno-common. Thanks much!