Fixes a crash in gnome-calculator when calculating nested pows.

Example test case:
  Input: 2³ ²
  Outcome: segfault
  Expected output: 512 (consistent with 2^3^2)

Checking against right.token in the calculatin allows us to know whether
we are in a nested calculation and should avoid atoi (as it should have
already been done) or not.
[l10n] Updated Turkish translation
Fix capitalization in Hungarian translation
Updated Norwegian bokmål translation
Fixed consecutive squaring
Fixed modulo calculations
Fixed for negative exponents in modular exponentiation
Improved factorization for numbers less than 2^64-1.
Fix for improving integer exponentiation
Releasing 3.9.2
update Simplified Chinese (zh_CN) translation
Added ReadMe