*: remove "pure" and "const" attributes from throwing functions

The "pure" and "const" attributes are not so well-defined, and a
recent clang version implements an optimization which pushes the
definition's boundary beyond what I believed it was.  clang now
assumes that functions declared "pure" cannot throw exceptions, even
if they lack the "noexcept" specification.

When compiled with this new clang version, MPD will crash randomly if
an exception happens to get thrown by such as "pure" function
(https://github.com/MusicPlayerDaemon/MPD/issues/41).

This commit removes all such misplaced "pure" and "const" attributes,
closing #41.

src/fs/AllocatedPath.hxx

@@ -159,7 +159,7 @@ public:
 	 * Convert a UTF-8 C string to an #AllocatedPath instance.
 	 * Throws a std::runtime_error on error.
 	 */
-	gcc_pure gcc_nonnull_all
+	gcc_nonnull_all
 	static AllocatedPath FromUTF8Throw(const char *path_utf8);
 
 	/**

src/fs/Charset.hxx

@@ -49,7 +49,7 @@ DeinitFSCharset() noexcept;
  *
  * Throws std::runtime_error on error.
  */
-gcc_pure gcc_nonnull_all
+gcc_nonnull_all
 PathTraitsUTF8::string
 PathToUTF8(PathTraitsFS::const_pointer_type path_fs);
 
@@ -58,7 +58,7 @@ PathToUTF8(PathTraitsFS::const_pointer_type path_fs);
  *
  * Throws std::runtime_error on error.
  */
-gcc_pure gcc_nonnull_all
+gcc_nonnull_all
 PathTraitsFS::string
 PathFromUTF8(PathTraitsUTF8::const_pointer_type path_utf8);
 

src/fs/io/BufferedReader.hxx

@@ -65,7 +65,6 @@ public:
 	 * it).  Throws std::runtime_error if not enough data is
 	 * available.
 	 */
-	gcc_pure
 	void *ReadFull(size_t size);
 
 	void Consume(size_t n) {

src/fs/io/FileReader.hxx

@@ -86,7 +86,6 @@ public:
 
 	void Close();
 
-	gcc_pure
 	FileInfo GetFileInfo() const;
 
 	gcc_pure