Need to handle when decompiler comments out external variables

[pdreiter]

Looks like hex-rays comments out external data declarations, which makes prd ignore them:

For example, from Rode0days 19.11 sqliteB4 function output_file_close:

//--------------------------------------------------------------------
// Data declarations

// extern struct _IO_FILE *stderr;
// extern struct _IO_FILE *stdout;

this is not processed correctly by PRD. (only effects 2 of 11615 functions tested)