Fix multiple calls of ggtags-show-definition

and misuse of pcase equality in ggtags-eldoc-function.

Fix ggtags-global-output to notice the problem of running multiple
processes.
Make ggtags-eldoc-function work better when no project root

Make M-. on #include line also triggers indexing project if not
already.
Revert "Fix ggtags-with-current-project to include GTAGSCONF"

This reverts commit e7c5371028912e07c37de2bf1c80c88bf51a1fea.
Make ggtags-use-project-gtagsconf work on remote projects

by using --gtagsconf instead of setenv'ing GTAGSCONF which does not
work on remote projects via tramp.
New macro ggtags-with-temp-message that reports execution time
Don't reply on excution order of filter and sentinel functions

There is no guarantee ggtags-global-handle-exit will be called after
ggtags-global-filter. So don't rely on this.

For example compile-goto-error on remote file (via tramp) might call
accept-process-output which allows process sentinel functions to run
per (info "(elisp)Sentinels").
Revert "Don't reply on excution order of filter and sentinel functions"

This reverts commit 03345fb9a25bc2cf09bebc2b96bd867d1c979cc2.

The commit appears to fix the bug because the idle timer does not run
in the *ggtags-global* buffer.
Properly fix the bug by delaying compilation finish functions

Function compilation-auto-jump may trigger running process sentinels
and thus ggtags-global-handle-exit causing itself to fail. This
happens fairly often on remote hosts via tramp due to
accept-process-output.
Doc fixes and add NEWS for 0.8.2
Fix warning "making variable buffer local while let-bound!"

for ggtags-global-output-format.
Rename ggtags-delete-tag-files to ggtags-delete-tags