v20170815

Release notes for eclib-20170815

Since release 20160720:

1. Modular symbols programs can use elliptic curve files instead of
   newform files at lower levels to eliminate oldforms.

2. fixed some memory leaks

3. fixed modular symbol scaling and improved handling of minus symbols,
   also allow basing of symbols at oo or 0. Also handle modular symbols
   for non-optimal curves. (These changes go hand-in-hand with changes
   in the Sage interface).

4. c++11 is now mandatory.

5. some fixes for clang (not yet complete).

6. Improved equivalence testing of quartics.

7. Improved handling of environment variables to set filenemes and
   change default settings, e.g. PARI_SIZE can now be used to handle
   larger integer factorizations.