Merge branch 'feature/eva/nested-widenings' into 'master'

[Eva] Improves widenings on nested loops

Closes Value/Value#122 and Value/Value#123

See merge request frama-c/frama-c!2046

tests/value/oracle/widen_on_non_monotonic.res.oracle

@@ -20,6 +20,7 @@
   Called from tests/value/widen_on_non_monotonic.i:71.
 [eva] tests/value/widen_on_non_monotonic.i:25: starting to merge loop iterations
 [eva] tests/value/widen_on_non_monotonic.i:23: starting to merge loop iterations
+[eva] tests/value/widen_on_non_monotonic.i:26: starting to merge loop iterations
 [eva:alarm] tests/value/widen_on_non_monotonic.i:27: Warning: 
   signed overflow. assert -2147483648 ≤ b - 1;
 [eva] Recording results for main1

tests/value/precise_locations.i

 /* run.config*
-   STDOPT: +"-then -inout -load-module report -report -then -plevel 250"
+   STDOPT: +"-eva-widening-period 3 -then -inout -load-module report -report -then -plevel 250"
 */
 
 struct s {