Use the term "macro expansion" instead of "pound literal".

Macros are a thing now, yo

Author: DougGregor

gyb_syntax_support/DeclNodes.py

@@ -898,7 +898,7 @@
 
     # e.g., "#embed("filename.txt")"
     Node('MacroExpansionDecl',
-         name_for_diagnostics="pound literal declaration", kind='Decl',
+         name_for_diagnostics="macro expansion", kind='Decl',
          traits=['FreestandingMacroExpansion'],
          children=[
              Child('PoundToken', kind='PoundToken',

gyb_syntax_support/ExprNodes.py

@@ -648,7 +648,7 @@
 
     # e.g., "#embed("filename.txt")"
     Node('MacroExpansionExpr',
-         name_for_diagnostics="pound literal expression", kind='Expr',
+         name_for_diagnostics="macro expansion expression", kind='Expr',
          traits=['FreestandingMacroExpansion'],
          children=[
              Child('PoundToken', kind='PoundToken',