*: add "noexcept" to many, many function prototypes

This eliminates some overhead, because the compiler doesn't need to
consider these functions throwing.

src/input/ThreadInputStream.cxx

@@ -124,7 +124,7 @@ ThreadInputStream::Check()
 }
 
 bool
-ThreadInputStream::IsAvailable()
+ThreadInputStream::IsAvailable() noexcept
 {
 	assert(!thread.IsInside());
 
@@ -158,7 +158,7 @@ ThreadInputStream::Read(void *ptr, size_t read_size)
 }
 
 bool
-ThreadInputStream::IsEOF()
+ThreadInputStream::IsEOF() noexcept
 {
 	assert(!thread.IsInside());