tgamma(3) from FreeBSD

[rudolf <netbsd%eq.cz@localhost>]

Hi,

I'd like to use ISO C99 tgamma(3) so I've prepared a patch for import of 
the function from FreeBSD:
http://software.eq.cz/tgamma.diff.txt

I've made the following steps:
- copy b_exp.c, b_log.c, b_tgamma.c s_tgammaf.c, mathimpl.h from FreeBSD 
(http://svnweb.freebsd.org/base/head/lib/msun/bsdsrc/) to src/lib/libm/src/
- comment out __FBSDID and add __RCSID in the imported files
- adjust path to math_private.h in mathimpl.h
- b_exp.c: use "static const double" instead of "const static double"
- add b_exp.c b_log.c b_tgamma.c s_tgammaf.c to src/lib/libm/Makefile
  and "mlink" lgamma.3 to tgamma.3, tgammaf.3
- add tgamma and tgammaf to src/include/math.h
- add relevant information from the FreeBSD manpage to lgamma.3

Please let me know if there are any issues with the import, I'd like to 
find this function in the upcoming NetBSD 6.0 release.

Thanks,

r.