Get back to 100% coverage

Closes #30

This is achieved by running libfuzzer with USE_32_BIT_VERSIONS={OFF,ON},
and then combining the corpora. I suspect that the problem earlier was
that we only had the 32 bit corpus but were measuring coverage for 64
bit in jenkins.

ConflictSet.cpp

@@ -1967,7 +1967,7 @@ bool checkMaxBetweenExclusive(Node *n, int begin, int end,
                               InternalVersionT readVersion) {
   assume(-1 <= begin);
   assume(begin <= 256);
-  assume(-1 <= end);
+  assume(0 < end);
   assume(end <= 256);
   assume(begin < end);
 
@@ -2039,9 +2039,6 @@ bool checkMaxBetweenExclusive(Node *n, int begin, int end,
   case Type_Node256: {
     static_assert(Node256::kMaxOfMaxTotalPages == 16);
     auto *self = static_cast<Node256 *>(n);
-    if (end <= 0) {
-      return true;
-    }
     const int firstPage = begin >> Node256::kMaxOfMaxShift;
     const int lastPage = (end - 1) >> Node256::kMaxOfMaxShift;
     // Check the only page if there's only one

Jenkinsfile

@@ -123,8 +123,7 @@ pipeline {
                 '''
                 recordCoverage qualityGates: [[criticality: 'NOTE', metric: 'MODULE']], tools: [[parser: 'COBERTURA', pattern: 'build/coverage.xml']]
                 sh '''
-                # Temporarily remove until we finish the transition to 32-bit versions
+                gcovr -f ConflictSet.cpp --fail-under-line 100 > /dev/null
-                # gcovr -f ConflictSet.cpp --fail-under-line 100 > /dev/null
                 '''
             }
         }