Always require a mask to get a temporary filename

If no mask is supplied or the mask is attached to the end of the filename, we end up with unexpected names like
  <system-temp-dir>\lyx_tmpdir.qHp780.vcr780_<mask>
instead of a temporary file in the lyx temporary directory like
  <system-temp-dir>\lyx_tmpdir.qHp780\<mask>.vcr780.

(cherry picked from commit 5e4e4b674c)

src/CutAndPaste.cpp

@@ -470,7 +470,7 @@ void putClipboard(ParagraphList const & paragraphs,
 	// some kind of garbage collection there, or a shared_ptr, then this
 	// would not be needed.
 	static Buffer * buffer = theBufferList().newBuffer(
-		FileName::tempName().absFileName() + "_clipboard.internal");
+		FileName::tempName("clipboard.internal").absFileName());
 	buffer->setUnnamed(true);
 	buffer->paragraphs() = paragraphs;
 	buffer->inset().setBuffer(*buffer);

src/LayoutFile.cpp

@@ -212,7 +212,7 @@ string layoutpost =
 
 LayoutFileIndex LayoutFileList::addEmptyClass(string const & textclass)
 {
-	FileName const tempLayout = FileName::tempName();
+	FileName const tempLayout = FileName::tempName("basic_layout");
 	ofstream ofs(tempLayout.toFilesystemEncoding().c_str());
 	// This writes a very basic class, but it also attempts to include 
 	// stdclass.inc. That would give us something moderately usable.

src/frontends/qt4/GuiWorkArea.cpp

@@ -1370,7 +1370,7 @@ bool GuiWorkArea::isFullScreen()
 EmbeddedWorkArea::EmbeddedWorkArea(QWidget * w): GuiWorkArea(w)
 {
 	buffer_ = theBufferList().newBuffer(
-		support::FileName::tempName().absFileName() + "_embedded.internal");
+		support::FileName::tempName("embedded.internal").absFileName());
 	buffer_->setUnnamed(true);
 	buffer_->setFullyLoaded(true);
 	setBuffer(*buffer_);

src/support/FileName.h

@@ -183,7 +183,7 @@ public:
 	/// \p mask must be in filesystem encoding, if it contains a
 	/// relative path, the template file will be created in the global
 	/// temporary directory as given by 'package().temp_dir()'.
-	static FileName tempName(std::string const & mask = empty_string());
+	static FileName tempName(std::string const & mask);
 	static FileName tempName(FileName const & temp_dir,
 		std::string const & mask);
 

status.20x

@@ -91,6 +91,9 @@ What's new
 - When configuring LyX, check for all LaTeX-packages LyX uses to display
   symbols (bug 8102).
 
+- Fix the naming of some temporary files such that they are created
+  in LyX's temporary directory.
+
 
 * USER INTERFACE