library: normalize stack and history allocation naming

Recent profiling and timings have resulted in improved
newlib performance. This patch completes that process.

It just normalizes naming conventions employed for all
allocations involving reaped stacks & history support.

The modules offering a 'reap' function will also offer
the now standardized corresponding STACKS_INCR define.

The modules which provide dynamic history support will
now have a separate #define called NEWOLD_INCR used in
allocations/reallocations. And, while values currently
are set equal to that STACKS_INCR value, in the future
some reason for divorcing those two may be discovered.

----------------------------- for future reference ---

In those modules which contain the STACKS_INCR #define
it is tempting to specify a large value so as to avoid
repeated calls to malloc/realloc. However, in doing so
an extra runtime price will be paid in 'cleanup_stack'
calls with any iterative programs like top or slabtop.

So, with the current values a balance has been sought.

Signed-off-by: Jim Warner <james.warner@comcast.net>

proc/diskstats.c

@@ -47,7 +47,7 @@
 #define DISKSTATS_FILE      "/proc/diskstats"
 #define SYSBLOCK_DIR        "/sys/block"
 
-#define STACKS_INCR         64
+#define STACKS_INCR         64           // amount reap stack allocations grow
 #define STR_COMPARE         strverscmp
 
 struct dev_data {