with gcc-10, build failed

[hbfl]

gcc-10 reported multiple definition. The attached patch solve this. Please confirm
mISDN-extern.txt

/usr/lib/gcc/i586-pc-linux-gnu/10/../../../../i586-pc-linux-gnu/bin/ld:
faxl3.o:/build/packages/BUILD/mISDNuser-2.1.1/capi20/alaw.h:6:
multiple definition of `slin2alaw';
daemon.o:/build/packages/BUILD/mISDNuser-2.1.1/capi20/alaw.h:6:
first defined here

/usr/lib/gcc/i586-pc-linux-gnu/10/../../../../i586-pc-linux-gnu/bin/ld:
faxl3.o:/build/packages/BUILD/mISDNuser-2.1.1/capi20/alaw.h:7:
multiple definition of `alaw2lin';
daemon.o:/build/packages/BUILD/mISDNuser-2.1.1/capi20/alaw.h:7:
first defined here

/usr/lib/gcc/i586-pc-linux-gnu/10/../../../../i586-pc-linux-gnu/bin/ld:
faxl3.o:/build/packages/BUILD/mISDNuser-2.1.1/capi20/alaw.h:5:
multiple definition of `lin2alaw';
daemon.o:/build/packages/BUILD/mISDNuser-2.1.1/capi20/alaw.h:5:
first defined here

/usr/lib/gcc/i586-pc-linux-gnu/10/../../../../i586-pc-linux-gnu/bin/ld:
alaw.o:/build/packages/BUILD/mISDNuser-2.1.1/capi20/alaw.h:5:
multiple definition of `lin2alaw';
daemon.o:/build/packages/BUILD/mISDNuser-2.1.1/capi20/alaw.h:5:
first defined here

/usr/lib/gcc/i586-pc-linux-gnu/10/../../../../i586-pc-linux-gnu/bin/ld:
alaw.o:/build/packages/BUILD/mISDNuser-2.1.1/capi20/alaw.h:6:
multiple definition of `slin2alaw';
daemon.o:/build/packages/BUILD/mISDNuser-2.1.1/capi20/alaw.h:6:
first defined here

/usr/lib/gcc/i586-pc-linux-gnu/10/../../../../i586-pc-linux-gnu/bin/ld:
alaw.o:/build/packages/BUILD/mISDNuser-2.1.1/capi20/alaw.h:7:
multiple definition of `alaw2lin';
daemon.o:/build/packages/BUILD/mISDNuser-2.1.1/capi20/alaw.h:7:
first defined here