chg: set blocks to keep to 0 for OM_NDEBUG
fix: StringSetS/StringAppendS/StringEndS may be used multiple times
fix: idKeepFirstK (Example_7_3_14)
fix: const
fix: memeory leak in matrix print
fix: memeory leak in versionString()
fix: configure syntax
fix: p_String: memory
chg: sigaction instead of signachg: sigaction instead of signall
fix: option(string) for libsing
add: ext_ref in ring struct
fix: double free in -v
chg: Tst/Plural/bern5_slimgb.* generated
chg:  ext_ref in ring struct: set to NULL for modified ring
chg: simplify signal handlers, use sigaction
opt.: int power with +/-1
fix: int power with +/-1
fix: use constants in +/-1^n
fix: warnings with table.h
Fix: avoid infinite recursion, if pyobject.so is broken