Fix memory leak on error (#307)

* Create test_memory_leak_on_error.js

* fix test_memory_leak_on_error.js

* Update test_memory_leak_on_error.js

* Update test_memory_leak_on_error.js

* Fix a memory leak in db.exec

When an error was thrown in db.exec, the allocated stack was never restored

* Enable assertions in debug builds

* Fix assertion error in debug builds

Fix Assertion failed: you need to wait for the runtime to be ready (e.g.
wait for main() to be called)

* Fix memory leak on error in Database.exec

Memory was leaked when Database.exec was run and the
execution threw an error

* Disable the memory leak test by default

The memory leak test is expensive, and we don't want to run it every
time

* Prevent several memory leaks on error

I did not manage to trigger OOM errors with them,
but db.run and db.each were also vulnerable to #306

* Check the compiled files in

Author: lovasoa

Makefile

@@ -41,6 +41,7 @@ EMFLAGS_OPTIMIZED= \
 
 EMFLAGS_DEBUG = \
 	-s INLINING_LIMIT=10 \
+	-s ASSERTIONS=1 \
 	-O1
 
 BITCODE_FILES = out/sqlite3.bc out/extension-functions.bc