Fix bug when parsing imports from 32bit PE.

There is a bug when parsing [1] which turns out to be incorrectly checking the
number of successfully parsed imported functions and not the number of parsed
attempts. This particular sample is badly malformed and is causing excessive
loops in the parser while attempting to parse invalid data. With this fix it
will finish in a few seconds on my laptop.

[1]: 9c8e4dfa84b1ce7e919964978d33eada266d58b2aacdbef44b0618cc178ea421

Author: wxsBSD

libyara/modules/pe/pe.c

@@ -939,7 +939,7 @@ static IMPORT_FUNCTION* pe_parse_import_descriptor(
 
     while (struct_fits_in_pe(pe, thunks32, IMAGE_THUNK_DATA32) &&
            yr_le32toh(thunks32->u1.Ordinal) != 0 &&
-           *num_function_imports < MAX_PE_IMPORTS)
+           parsed_imports < MAX_PE_IMPORTS)
     {
       char* name = NULL;
       uint16_t ordinal = 0;