Add regression test for crash 10.

Author: threeifbyair

regression-tests/pure2-bugfix-for-bad-capture.cpp2

@@ -0,0 +1,3 @@
+crash_10: (foo: i32) = {
+  assert( 10LL as i32 == foo$);
+}

regression-tests/test-results/pure2-bugfix-for-bad-capture.cpp2.output

@@ -0,0 +1,4 @@
+pure2-bugfix-for-bad-capture.cpp2...
+pure2-bugfix-for-bad-capture.cpp2(2,29): error: $ (capture) cannot appear here - it must appear in an anonymous expression function, a postcondition, or an interpolated string literal (at '$')
+pure2-bugfix-for-bad-capture.cpp2(2,23): error: expected ')' at the end of the contract (at '==')
+