add bad syntax tests for PEP 492

tests/errors/pep492_badsyntax_async1.pyx

+# mode: error
+# tag: pep492, async
+
+async def foo():
+    def foo(a=await list()):
+        pass
+
+_ERRORS = """
+5:14: 'await' not supported here
+"""

tests/errors/pep492_badsyntax_async2.pyx

+# mode: error
+# tag: pep492, async
+
+async def foo():
+    def foo(a:await list()):
+        pass
+
+_ERRORS = """
+5:14: 'await' not supported here
+5:14: 'await' not supported here
+"""

tests/errors/pep492_badsyntax_async3.pyx

+# mode: error
+# tag: pep492, async
+
+async def foo():
+    [i async for i in els]
+
+_ERRORS = """
+5:7: Expected ']', found 'async'
+"""

tests/errors/pep492_badsyntax_async4.pyx

+# mode: error
+# tag: pep492, async
+
+async def foo():
+    async def foo(): await list()
+
+_ERRORS = """
+# ???  - this fails in CPython, not sure why ...
+"""

tests/errors/pep492_badsyntax_async5.pyx

+# mode: error
+# tag: pep492, async
+
+def foo():
+    await list()
+
+_ERRORS = """
+5:10: Syntax error in simple statement list
+"""

tests/errors/pep492_badsyntax_async6.pyx

+# mode: error
+# tag: pep492, async
+
+async def foo():
+    yield
+
+_ERRORS = """
+5:4: 'yield' not allowed in async coroutines (use 'await')
+5:4: 'yield' not supported here
+"""

tests/errors/pep492_badsyntax_async7.pyx

+# mode: error
+# tag: pep492, async
+
+async def foo():
+    yield from []
+
+_ERRORS = """
+5:4: 'yield from' not supported here
+5:4: 'yield' not allowed in async coroutines (use 'await')
+"""

tests/errors/pep492_badsyntax_async8.pyx

+# mode: error
+# tag: pep492, async
+
+async def foo():
+    await await fut
+
+_ERRORS = """
+5:10: Expected an identifier or literal
+"""

tests/errors/pep492_badsyntax_async9.pyx

+# mode: error
+# tag: pep492, async
+
+async def foo():
+    await
+
+_ERRORS = """
+5:9: Expected an identifier or literal
+"""