NEWS: Rename "Changes since GDB 7.6" into "Changes in GDB 7.7"

gdb/ChangeLog:

        * NEWS: Change "Changes since GDB 7.6" to "Changes in GDB 7.7".
Set GDB version number to 7.7.

gdb/ChangeLog:

	* version.in: Set GDB version number to 7.7.
Document the GDB 7.7 release in gdb/ChangeLog

gdb/ChangeLog:

	GDB 7.7 released.
Bump GDB version number to 7.7.0.DATE-cvs.

gdb/ChangeLog:

	* version.in: Set GDB version number to 7.7.0.DATE-cvs.
Automatic date update in version.in