updated __attribute__ and __declspec support

Author: WalterBright

spec/importc.dd

@@ -633,6 +633,9 @@ $(H2 $(LNAME2 gnu-clang-extensions, Gnu and Clang Extensions))
     $(LI `__attribute__((naked))`)
     $(LI `__attribute__((noinline))`)
     $(LI $(RELATIVE_LINK2 noreturn, `__attribute__((noreturn))`))
+    $(LI `__attribute__((nothrow))`)
+    $(LI `__attribute__((pure))`)
+    $(LI `__attribute__((vector_size(N)))`)
     $(LI others are ignored)
     )
 
@@ -677,13 +680,15 @@ $(H2 $(LNAME2 visualc-extensions, Visual C Extensions))
     $(P The following $(LINK2 https://learn.microsoft.com/en-us/cpp/cpp/declspec?view=msvc-170, `__declspec` extensions):)
 
     $(OL
+    $(LI `__declspec()`)
     $(LI `__declspec(align(N))`)
     $(LI `__declspec(deprecated)`)
     $(LI `__declspec(dllexport)`)
     $(LI `__declspec(dllimport)`)
     $(LI `__declspec(naked)`)
     $(LI `__declspec(noinline)`)
     $(LI `__declspec(noreturn)`)
+    $(LI `__declspec(nothrow)`)
     $(LI `__declspec(thread)`)
     $(LI others are ignored)
     )