[Patch, PowerPC/Darwin] Fix library export of long double symbols.

During 8.x, the rs6000 target-specific mangling was reorganised which uncovered
a long-standing bug in Darwin’s mangling for ‘IBM’ long double.  Now the symbols
are correctly mangled, and we end up with a bunch of test link fails.

This patch adds the necessary subset of the Linux long double exports to Darwin’s
export table.

2018-12-22  Iain Sandoe  <iain@sandoe.co.uk>

	* /config/os/bsd/darwin/ppc-extra.ver: Append long double symbols.

From-SVN: r267358

libstdc++-v3/ChangeLog

+2018-12-22  Iain Sandoe  <iain@sandoe.co.uk>
+
+	* /config/os/bsd/darwin/ppc-extra.ver: Append long double symbols.
+
 2018-12-20  Jonathan Wakely  <jwakely@redhat.com>
 
 	* testsuite/27_io/filesystem/operations/proximate.cc: Fix test for

libstdc++-v3/config/os/bsd/darwin/ppc-extra.ver

   __eprintf;
+# 3.4
+  _ZNSt14numeric_limitsIgE*;
+  _ZNSirsERg;
+  _ZNSolsEg;
+  _ZNSt13basic_istreamIwSt11char_traitsIwEErsERg;
+  _ZNSt13basic_ostreamIwSt11char_traitsIwEElsEg;
+  _ZSt14__convert_to_vIgEvPKcRT_RSt12_Ios_IostateRKP*;
+  _ZStlsIg[cw]St11char_traitsI[cw]EERSt13basic_ostreamIT0_T1_ES6_RKSt7complexIT_E;
+  _ZStrsIg[cw]St11char_traitsI[cw]EERSt13basic_istreamIT0_T1_ES6_RSt7complexIT_E;
+# 3.4.7
+  _ZNSi10_M_extractIgEERSiRT_;
+  _ZNSt13basic_istreamIwSt11char_traitsIwEE10_M_extractIgEERS2_RT_;
+  _ZNSo9_M_insertIgEERSoT_;
+  _ZNSt13basic_ostreamIwSt11char_traitsIwEE9_M_insertIgEERS2_T_;
+# 3.4.10
+  _ZNKSt3tr14hashIgEclEg;
+  _ZNKSt4hashIgEclEg;
+# ldbl 1.3
+  _ZT[IS]g;
+  _ZT[IS]Pg;
+  _ZT[IS]PKg;