tokenizer is required, fix #1

[remicollet]

Detected by phpcompatinfo analyse

 $ phpcompatinfo analyser:run php/src/internal/

 Data Source Analysed

 Directories                                          2
 Files                                                4

 Extensions Analysis

     Extension Matches REF       EXT min/Max PHP min/Max PHP all 
     Core              Core      5.1.0       5.1.0               
     pcre              pcre      4.0.0       4.0.0               
     standard          standard  5.0.0       5.0.0               
     tokenizer         tokenizer 5.4.0       5.4.0               
     Total [4]                               5.4.0               
 ...

[flaupretre]

Thanks for this. Didn't think about dependencies from PHP code. Will add the same for pcre.