gdb: use the PKGVERSION and BUGURL options

This patch makes gdb benefit from the TOOLCHAIN_PKGVERSION and
TOOLCHAIN_BUGURL options.

Signed-off-by: "Benoît THÉBAUDEAU" <benoit.thebaudeau@advansee.com>

 reporter_name="Yann E. MORIN"

 reporter_url="http://ymorin.is-a-geek.org/projects/crosstool"

 reporter_comment="Experimental toolchain for ARM cortex-m3 in Thumb-only, noMMU, and newlib."