Linux: fix CentOS 6 build with GCC 4.4

CentOS 6 builds VeraCrypt with GCC 4.4.7 and -std=c++0x. That compiler does not support range-based for loops, and its libstdc++ does not provide std::string::back() or std::string::pop_back().

Avoid those constructs in the affected Unix/Linux code paths: use VeraCrypt's existing foreach helper when iterating PKCS#11 object handles, and use indexing plus erase() when trimming trailing slashes from PATH entries.

This keeps the code valid for newer Linux toolchains while restoring compatibility with the CentOS 6 build environment.

src/Common/SecurityToken.cpp

@@ -220,7 +220,7 @@ namespace VeraCrypt
 				throw;
 			}
 
-			for(const CK_OBJECT_HANDLE & dataHandle: GetObjects(slotId, CKO_DATA))
+			foreach(const CK_OBJECT_HANDLE & dataHandle, GetObjects(slotId, CKO_DATA))
 			{
 				SecurityTokenKeyfile keyfile;
 				keyfile.Handle = dataHandle;