buffer truncation looking up MIME types

Per subsequent discussions, switching to BString::SetToFormat which completely
eliminates the need for allocating a fixed buffer and will avoid truncation.

Change-Id: Ic2a803594877a0a6fb1bc4eba937268351e6f45c
Reviewed-on: https://review.haiku-os.org/c/haiku/+/8837
Haiku-Format: Haiku-format Bot <[email protected]>
Reviewed-by: Adrien Destugues <[email protected]>
Tested-by: Commit checker robot <[email protected]>

src/kits/storage/mime/AssociatedTypes.cpp

@@ -375,9 +375,8 @@ AssociatedTypes::BuildAssociatedTypesTable()
 								if (subEntry.GetName(subtype) == B_OK) {
 									BPrivate::Storage::to_lower(subtype);
 
-									char fulltype[B_PATH_NAME_LENGTH];
-									snprintf(fulltype, B_PATH_NAME_LENGTH, "%s/%s",
-										supertype, subtype);
+									BString fulltype;
+									fulltype.SetToFormat("%s/%s", supertype, subtype);
 
 									// Process the subtype
 									ProcessType(fulltype);

src/kits/storage/mime/SnifferRules.cpp

@@ -373,9 +373,8 @@ SnifferRules::BuildRuleList()
 								if (subEntry.GetName(subtype) == B_OK) {
 									BPrivate::Storage::to_lower(subtype);
 
-									char fulltype[B_PATH_NAME_LENGTH];
-									snprintf(fulltype, B_PATH_NAME_LENGTH, "%s/%s",
-										supertype, subtype);
+									BString fulltype;
+									fulltype.SetToFormat("%s/%s", supertype, subtype);
 
 									// Process the subtype
 									ProcessType(fulltype, &bytesNeeded);