Activate more SMT2 tests

Some tests are now working with the SMT2 backend and can be activated.

Author: romainbrenguier

regression/cbmc/Array_operations1/test.desc

@@ -1,4 +1,4 @@
-CORE broken-smt-backend
+CORE
 main.c
 
 ^EXIT=10$

regression/cbmc/Float-equality1/test_no_equality.desc

@@ -1,4 +1,4 @@
-CORE broken-smt-backend
+CORE
 main.c
 
 ^EXIT=0$

regression/cbmc/compact-trace/test.desc

@@ -1,4 +1,4 @@
-CORE broken-smt-backend
+CORE
 main.c
 --compact-trace
 activate-multi-line-match

regression/cbmc/union6/test.desc

@@ -1,4 +1,4 @@
-CORE broken-smt-backend
+CORE
 main.c
 --little-endian
 ^EXIT=0$

regression/cbmc/union7/test.desc

@@ -1,4 +1,4 @@
-CORE broken-smt-backend
+CORE
 main.c
 --big-endian
 ^EXIT=0$