fix -Wimplicit-int for ifsense
    
    fixes:
    xmlif/xmlif.l:46:8: warning: type defaults to ‘int’ in declaration of ‘ifsense’ [-Wimplicit-int]
       46 | static ifsense;                 /* sense of last `if' or unless seen */
          |        ^~~~~~~
    
    Signed-off-by: Thomas Kuehne <thomas@kuehne.cn>