[PATCH] tau support in math.h

[Joseph S. Myers]

The M_* constants are conditional on [__USE_BSD || __USE_XOPEN], plus 
[__USE_GNU] long double versions; nothing should be added that's not in 
those standards.  If a future version of POSIX adds a new M_* constant 
(whether XSI-conditional or otherwise), then glibc would add it under 
appropriate conditions for that version of POSIX (and, as needed, a long 
double version under __USE_GNU), not in the existing block of values.  I 
don't believe it's appropriate to add new constants otherwise, especially 
not when, as noted, they are trivially derived from other constants 
already present with no loss of accuracy.

-- 
Joseph S. Myers
joseph@codesourcery.com