library: make dynamic buffer management more efficient

library: make dynamic buffer management more efficient

When dynamic buffers were recently introduced for read
of the status, stat and statm subdirectories one extra
call to read() was required for end-of-file detection.

This patch avoids most all such extra calls to read().

Additionally, the frequency of memory reallocations is
reduced by overallocating each increase more than 25%.

Reference)s):
commit a45dace4b82c9cdcda7020ca5665153b1e81275f

Signed-off-by: Jim Warner <james.warner@comcast.net>
Signed-off-by: Craig Small <csmall@enc.com.au>