fix severity from string functions

Strings that were a case-insensitive prefix of a valid severity string
were incorrectly accepted due to an incomplete case-insensitive comparison
implementation. This change corrects this and adds tests to prevent
regression.

src/strhelper.c

@@ -85,10 +85,11 @@ strncasecmp_custom( const char *s1, const char *s2, size_t n ) {
   if (n != 0) {
     do {
       if (tolower(*s1) != tolower(*s2++))
-        return tolower(*s1) - tolower(*--s2);
+        return tolower(*--s2) - tolower(*s1);
       if (*s1++ == '\0')
         break;
     } while (--n != 0);
+    if(*s2 != '\0') return tolower(*s2) - tolower(*s1);
   }
   return 0;
-}
+}

test/function/severity.cpp

@@ -113,4 +113,28 @@ namespace {
     EXPECT_EQ( result, -1 );
   }
 
+  TEST( GetSeverityEnumFromBuffer, IncompleteSeverity ) {
+    enum stumpless_severity result = stumpless_get_severity_enum( "war" );
+    EXPECT_EQ( result, -1 );
+
+    result = stumpless_get_severity_enum( "not" );
+    EXPECT_EQ( result, -1 );
+  }	
+
+
+  TEST( GetSeverityEnumFromBuffer, OverextendedSeverity ) {
+    enum stumpless_severity result = stumpless_get_severity_enum( "warnings are neat" );
+    EXPECT_EQ( result, -1 );
+
+    result = stumpless_get_severity_enum( "notices are bad" );
+    EXPECT_EQ( result, -1 );
+
+    result = stumpless_get_severity_enum( "panic you should not" );
+    EXPECT_EQ( result, -1 );
+
+  }	
+
+
+
+
 }