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

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

src/lib/icu/Collate.cxx

@@ -65,7 +65,7 @@ IcuCollateInit()
 }
 
 void
-IcuCollateFinish()
+IcuCollateFinish() noexcept
 {
 	assert(collator != nullptr);
 
@@ -76,7 +76,7 @@ IcuCollateFinish()
 
 gcc_pure
 int
-IcuCollate(const char *a, const char *b)
+IcuCollate(const char *a, const char *b) noexcept
 {
 #if !CLANG_CHECK_VERSION(3,6)
 	/* disabled on clang due to -Wtautological-pointer-compare */

src/lib/icu/Collate.hxx

@@ -32,11 +32,11 @@ void
 IcuCollateInit();
 
 void
-IcuCollateFinish();
+IcuCollateFinish() noexcept;
 
 gcc_pure gcc_nonnull_all
 int
-IcuCollate(const char *a, const char *b);
+IcuCollate(const char *a, const char *b) noexcept;
 
 gcc_pure gcc_nonnull_all
 AllocatedString<char>