New user variable ggtags-global-use-color
Implement feature #43: Jump to match from search history

Rename ggtags-auto-jump-to-first-match to ggtags-auto-jump-to-match
accordingly.
Fix warning: Making variable buffer-local while let-bound!

for ggtags-auto-jump-to-match-target.
Disable ggtags-navigation-mode in ggtags-global-mode.
Use compilation-auto-jump in ggtags-global-filter

to correctly set point in that window.
Disable ggtags-navigation-mode at the right time

Otherwise the *ggtags-global* buffer is not displayed until
compilation finishes.
Rename ggtags-handle-single-match to ggtags-global-handle-exit
Fix ggtags-navigation-mode-abort when pop-tag-mark errs
Fix #44: New variable ggtags-enable-navigation-keys

to control ggtags-navigation-map. Using ggtags-navigation-mode is
unsafe because it is used more than controlling ggtags-navigation-map.

Affect #40: ggtags-suppress-navigation-keys is removed; use
ggtags-enable-navigation-keys instead.