Increase max embedded objects limit from 10 -> 16

By limiting the embedded file recognition in embedded files, we detect
fewer embedded files overall.

For example, imagine a PE with a structure of embedded files like so:

outer pe:
 emb. file #1: valid pe #1
 emb. file #2: valid pe #2
 emb. file #3: valid pe #3
 emb. file #4: false positive for pe
 emb. file #5: false positive for pe
 emb. file #6: false positive for pe
 emb. file #7: false positive for pe
 emb. file #8: false positive for pe
 emb. file #9: false positive for pe
 emb. file #10: false positive for pe
 emb. file #10: valid pe #4

With an embedded objects limit of 10, we won't extract that 4th valid PE
file.

However, previous we allowed detection of embedded files within embedded
files, so ClamAV mistook the above structure for something like this:

outer pe:
 emb. file #1: valid pe #1
   emb. file #1: valid pe #2
     emb. file #1: valid pe #3
       emb. file #1: false positive for pe
       emb. file #2: false positive for pe
       emb. file #3: false positive for pe
       emb. file #4: false positive for pe
       emb. file #5: false positive for pe
       emb. file #6: false positive for pe
       emb. file #7: false positive for pe
       emb. file #8: valid pe #4

As you can see, this is able to find and scan that 4th PE file without
exceeding an embedded object limit of 10.

The old way of detecting embedded files within embedded files has other
drawbacks and is obviously inaccurate in terms of the actual file
structure. But it did have that going for it.

Anyways, to improve detection, this PR bumps the embedded objects limit
to 16. I think that's okay since we've added header checks for several
types like PE's, and have also removed the need to drop embedded PE
files to a temp file for each scan.

CLAM-2897

Author: val-ms

libclamav/filetypes.h

@@ -33,7 +33,7 @@
 #define MAGIC_BUFFER_SIZE 1028
 
 #define CL_TYPENO 500
-#define MAX_EMBEDDED_OBJ 10
+#define MAX_EMBEDDED_OBJ 16
 
 typedef enum cli_file {
     CL_TYPE_ANY        = 0,