fix(io): consider cpp2 line ending in comment

regression-tests/mixed-bugfix-for-cpp2-comment-cpp1-sequence.cpp2

@@ -0,0 +1,2 @@
+x: i32 = 0; // ugh
+int main() { }

regression-tests/test-results/mixed-bugfix-for-cpp2-comment-cpp1-sequence.cpp

@@ -0,0 +1,21 @@
+
+
+//=== Cpp2 type declarations ====================================================
+
+
+#include "cpp2util.h"
+
+
+
+//=== Cpp2 type definitions and function declarations ===========================
+
+#line 1 "mixed-bugfix-for-cpp2-comment-cpp1-sequence.cpp2"
+extern cpp2::i32 x;
+int main() { }
+            // ugh
+
+//=== Cpp2 function definitions =================================================
+
+#line 1 "mixed-bugfix-for-cpp2-comment-cpp1-sequence.cpp2"
+cpp2::i32 x {0}; 
+

regression-tests/test-results/mixed-bugfix-for-cpp2-comment-cpp1-sequence.cpp2.output

@@ -0,0 +1,2 @@
+mixed-bugfix-for-cpp2-comment-cpp1-sequence.cpp2... ok (mixed Cpp1/Cpp2, Cpp2 code passes safety checks)
+

source/io.h

@@ -623,7 +623,7 @@ auto process_cpp_line(
                             }
                         }
                     }
-                    
+
                 break;case '\"':
                     //  If this isn't an escaped quote, toggle string literal state
                     if (
@@ -746,7 +746,7 @@ auto process_cpp2_line(
                 }
 
             break;case '/':
-                if (prev == '/') { in_comment = false; return false; }
+                if (prev == '/') { in_comment = false; return found_end; }
 
             break;case '"':
                 if (prev != '\\') { in_string_literal = true; }