gcc 4.2.1: fix undefined reference to fmsub in C++ programs with soft float

Fix 'undefined reference to fmsub' linking errors with C++ programs
when soft float is enabled. Patch by b5331.

Closes #1588.

toolchain/gcc/4.2.1/920-soft-float.patch

@@ -0,0 +1,21 @@
+diff -uNpr gcc-4.2.1_orig/gcc/config/rs6000/darwin-ldouble.c gcc-4.2.1/gcc/config/rs6000/darwin-ldouble.c
+--- gcc-4.2.1_orig/gcc/config/rs6000/darwin-ldouble.c	2007-03-05 11:54:00.000000000 -0500
++++ gcc-4.2.1/gcc/config/rs6000/darwin-ldouble.c	2008-01-31 17:51:24.000000000 -0500
+@@ -70,6 +70,8 @@ Software Foundation, 51 Franklin Street,
+    but GCC currently generates poor code when a union is used to turn
+    a long double into a pair of doubles.  */
+ 
++#if defined (_SOFT_FLOAT) && defined (__LONG_DOUBLE_128__)
++
+ long double __gcc_qadd (double, double, double, double);
+ long double __gcc_qsub (double, double, double, double);
+ long double __gcc_qmul (double, double, double, double);
+@@ -219,8 +221,6 @@ __gcc_qdiv (double a, double b, double c
+   return z.ldval;
+ }
+ 
+-#if defined (_SOFT_FLOAT) && defined (__LONG_DOUBLE_128__)
+-
+ long double __gcc_qneg (double, double);
+ int __gcc_qeq (double, double, double, double);
+ int __gcc_qne (double, double, double, double);