Add tests for functions without end marker. NFC (#1405)

Inspired by this downstream test in wabt:
WebAssembly/wabt#1775

Fixes: #1404

Author: sbc100

test/core/binary.wast

@@ -368,6 +368,62 @@
   "integer too large"
 )
 
+;; Function with missing end marker (between two functions)
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\01\04\01\60\00\00"       ;; Type section: 1 type
+    "\03\03\02\00\00"          ;; Function section: 2 functions
+    "\0a\0c\02"                ;; Code section: 2 functions
+    ;; function 0
+    "\04\00"                   ;; Function size and local type count
+    "\41\01"                   ;; i32.const 1
+    "\1a"                      ;; drop
+    ;; Missing end marker here
+    ;; function 1
+    "\05\00"                   ;; Function size and local type count
+    "\41\01"                   ;; i32.const 1
+    "\1a"                      ;; drop
+    "\0b"                      ;; end
+  )
+  "END opcode expected"
+)
+
+;; Function with missing end marker (at EOF)
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\01\04\01\60\00\00"       ;; Type section: 1 type
+    "\03\02\01\00"             ;; Function section: 1 function
+    "\0a\06\01"                ;; Code section: 1 function
+    ;; function 0
+    "\04\00"                   ;; Function size and local type count
+    "\41\01"                   ;; i32.const 1
+    "\1a"                      ;; drop
+    ;; Missing end marker here
+  )
+  "unexpected end of section or function"
+)
+
+;; Function with missing end marker (at end of code sections)
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\01\04\01\60\00\00"       ;; Type section: 1 type
+    "\03\02\01\00"             ;; Function section: 1 function
+    "\0a\06\01"                ;; Code section: 1 function
+    ;; function 0
+    "\04\00"                   ;; Function size and local type count
+    "\41\01"                   ;; i32.const 1
+    "\1a"                      ;; drop
+    ;; Missing end marker here
+    "\0b\03\01\01\00"          ;; Data section
+  )
+  ;; The spec interpreter consumes the `\0b` (data section start) as an
+  ;; END instruction (also happens to be `\0b`) and reports the code section as
+  ;; being larger than declared.
+  "section size mismatch"
+)
 
 ;; Unsigned LEB128 must not be overlong
 (assert_malformed