[numeric.limits.members] Replaced usage of 'mantissa' with 'significand' according to

SO/IEC/IEEE 60559:2008

Author: MFHava

source/support.tex

@@ -1069,7 +1069,7 @@
 
 \pnum
 For floating-point types, the number of \tcode{radix} digits in the
-mantissa.
+significand.
 \begin{footnote}
 Equivalent to \tcode{FLT_MANT_DIG}, \tcode{DBL_MANT_DIG},
 \tcode{LDBL_MANT_DIG}.