Change "retain" to "ref" in various comments.

Author: https://github.com/awesomekling
Commit: https://github.com/SerenityOS/serenity/commit/c26e3ce86b6

AK/AKString.h

@@ -17,7 +17,7 @@ namespace AK {
 // Note that StringImpl is an immutable object that cannot shrink or grow.
 // Its allocation size is snugly tailored to the specific string it contains.
 // Copying a String is very efficient, since the internal StringImpl is
-// retainable and so copying only requires modifying the retain count.
+// retainable and so copying only requires modifying the ref count.
 //
 // There are three main ways to construct a new String:
 //

Kernel/Process.cpp

@@ -2031,9 +2031,9 @@ size_t Process::amount_resident() const
 size_t Process::amount_shared() const
 {
     // FIXME: This will double count if multiple regions use the same physical page.
-    // FIXME: It doesn't work at the moment, since it relies on PhysicalPage retain counts,
+    // FIXME: It doesn't work at the moment, since it relies on PhysicalPage ref counts,
     //        and each PhysicalPage is only reffed by its VMObject. This needs to be refactored
-    //        so that every Region contributes +1 retain to each of its PhysicalPages.
+    //        so that every Region contributes +1 ref to each of its PhysicalPages.
     size_t amount = 0;
     for (auto& region : m_regions) {
         amount += region->amount_shared();

Kernel/TTY/MasterPTY.cpp

@@ -63,8 +63,8 @@ void MasterPTY::notify_slave_closed(Badge<SlavePTY>)
 #ifdef MASTERPTY_DEBUG
     dbgprintf("MasterPTY(%u): slave closed, my retains: %u, slave retains: %u\n", m_index, ref_count(), m_slave->ref_count());
 #endif
-    // +1 retain for my MasterPTY::m_slave
-    // +1 retain for FileDescription::m_device
+    // +1 ref for my MasterPTY::m_slave
+    // +1 ref for FileDescription::m_device
     if (m_slave->ref_count() == 2)
         m_slave = nullptr;
 }

Servers/WindowServer/WSClientConnection.cpp

@@ -491,7 +491,7 @@ void WSClientConnection::handle_request(const WSAPIGetClipboardContentsRequest&)
         response.clipboard.contents_size = WSClipboard::the().size();
 
         // FIXME: This is a workaround for the fact that SharedBuffers will go away if neither side is retaining them.
-        //        After we respond to GetClipboardContents, we have to wait for the client to retain the buffer on his side.
+        //        After we respond to GetClipboardContents, we have to wait for the client to ref the buffer on his side.
         m_last_sent_clipboard_content = move(shared_buffer);
     }
     post_message(response);