todo: back-port some fixes

[bnoordhuis]

Minor correctness fixes but pretty intrusive and don't cherry-pick cleanly:

• bellard/quickjs@10fc744 (probably the easiest one)
• bellard/quickjs@af30861
• bellard/quickjs@f25e5d4

There's also bellard/quickjs@efdb722 for a test that does eval("import('./module-code_FIXTURE.js');") that I fixed... quite differently... in 64c9ac5 :-)

[saghul]

First: #534
Middle one: #531
Last one: #533

[saghul]

All done!