Fix problems with losing tokens in the jobserver, reported by Grant

Taylor.  There are two forms of this: first, it was possible to lose
tokens when using -j and -l at the same time, because waiting jobs were
not checked when determining whether any jobs were outstanding.  Second,
if you had an exported recursive variable that contained a $(shell ...)
function there is a possibility to lose tokens, since a token was taken
but the child list was not updated until after the shell function was
complete.

To resolve this I introduced a new variable that counted the number of
tokens we have obtained, rather than checking whether there were any
children on the list.  I also added some sanity checks to make sure we
weren't writing back too many or not enough tokens.  And, the master
make will drain the token pipe before exiting and compare the count of
tokens at the end to what was written there at the beginning.

Also:
  * Ensure a bug in the environment (missing "=") doesn't cause make to core.
  * Rename the .DEFAULT_TARGET variable to .DEFAULT_GOAL, to match the
    terminology in the documentation and other variables like MAKECMDGOALS.
  * Add documentation of the .DEFAULT_GOAL special variable.

Still need to document the secondary expansion stuff...

1 files changed, 2 insertions, 3 deletions

diff --git a/NEWS b/NEWS
index 3a350da..5ee75ac 100644
--- a/NEWS
+++ b/NEWS
@@ -52,9 +52,8 @@ Version 3.81beta3
 * New special variables available in this release:
    - .FEATURES: Contains a list of special features available in this
      version of GNU make.
-   - .DEFAULT_TARGET: Contains the name of the default target make will
-     use if no targets are provided on the command line.  It can be set
-     to change the default target.
+   - .DEFAULT_GOAL: Set the name of the default goal make will
+     use if no goals are provided on the command line.
    - New automatic variable: $| (added in 3.80, actually): contains all
      the order-only prerequisites defined for the target.