Fix incorrect Alpha status to Stable
Merge branch 'fix-mainpage-alpha-status'
Add duk_get_error_code() and duk_is_error() to API
Test for duk_get_error_code() and duk_is_error()
API docs for duk_is_error/duk_get_error_code
Cmdline: read 'stack' only if value is an error
Update API doc defines (DUK_ERR_NONE)
Release note: duk_is_error, duk_get_error_code
Merge branch 'api-get-error-code-is-error'

Add duk_get_error_code() and duk_is_error() API calls for more convenient
error handling.
Sandbox allocator bug fixes
Example allocator with alloc/realloc/free logging
Example allocator with wiping/red zones
Add logging/torture example allocator to dist
Add logged/torture allocator support to cmdline

Enable alloc logging/torture support in 'duk' by default.  This is only for
the Duktape repo 'duk' build, not for the dist version of it.
Release note: logging/torture allocator
Merge branch 'add-example-allocators'

Add two example allocators to the distributable:

- A logging allocator writes alloc/realloc/free sizes and results to
  /tmp/duk-alloc-log.txt.  The log includes previous allocation size
  for realloc() and free() so that the memory behavior can be played
  back and used for e.g. optimizing allocator pool sizes.

- A torture allocator uses red zones to detect out-of-bound writes,
  inits data to a non-zero value, and wipes freed memory areas so
  accidental reads after freeing are detected more easily.  This
  allocator can be used on almost any target to detect basic issues
  and is useful especially when Valgrind doesn't work on the target.

Also fix some NULL checks in sandbox allocator example.
Add =introduced version to API call files
Add =introduced as a fake tag for now in API doc
Merge branch 'add-api-call-versioninfo'

Add =introduced version to API call docs.  Reserve =deprecated and =removed
for marking deprecation and removal versions.

For now, render =introduced as a fake tag in the API doc entry.