Merge elftoolchain r3877 (by jkoshy):

Incorporate fixes from Dimitry Andric:

- Use a BUFFER_GROW() macro to avoid rounding errors in capacity
  calculations.
- Fix a bug introduced in [r3531].
- Fix handling of nested template parameters.

Ticket:	#581

This should fix a number of assertions on elftoolchain's cxxfilt, and
allow it to correctly demangle several names that it could not handle
before.

Obtained from: https://sourceforge.net/p/elftoolchain/code/3877/
PR: 250702
MFC after: 3 days