Few configure.ac adjustments

- Use the extensions autoconf finds for object and executable files.
- Remove the sorev variable, and replace SOREV definition with sorev's.
- Default to je_ prefix on win32.

include/jemalloc/internal/util.h

@@ -161,9 +161,9 @@ get_errno(void)
 {
 
 #ifdef _WIN32
-	return GetLastError();
+	return (GetLastError());
 #else
-	return errno;
+	return (errno);
 #endif
 }
 #endif