Fix #1016: Respect NODE_PATH from the environment.

In order to be able to use normal Node.js modules, the NodeJSEnv must
respect NODE_PATH from the environment and properly merge it with its
own provided library path (for CommonJS-style includes).
Fix #997: Limited support for in-pattern regex flags.
Merge pull request #1019 from gzm0/in-regex-flags

Fix #997: Limited support for in-pattern regex flags.
Add auto-generated tests for source maps.
Fix #1011: Correctly print -0.0 when linking in JS.
Merge pull request #1022 from gzm0/fix-tree-printer-zero

Fix #1011: Correctly print -0.0 when linking in JS.
Merge pull request #1007 from gzm0/sourceMapTests

Added auto-generated tests for source maps.