qucs: Fix simulator crash

Avoid undefined behaviour while traversing and modifying a std::list.
Patch has been reported to Qucs upstream.

Fixes https://github.com/voidlinux/void-packages/issues/7604

srcpkgs/qucs/patches/qucsator-fix-list-traversion.patch

@@ -0,0 +1,17 @@
+--- qucs-core/src/net.cpp.org	2017-09-13 20:47:24.863069583 +0200
++++ qucs-core/src/net.cpp	2017-09-10 00:16:48.863636748 +0200
+@@ -350,7 +350,13 @@
+ void net::sortChildAnalyses (analysis * parent) {
+   ptrlist<analysis> * alist = parent->getAnalysis ();
+   if (alist != nullptr) {
+-    for (auto *a: *alist) {
++
++    for (auto it = alist->begin(); it != alist->end(); /* empty */) {
++      // Copy the value of the element (a pointer), and advance the
++      // iterator prior to manipulating the list.
++      analysis *a = *it;
++      ++it;
++
+       if (a->getType () == ANALYSIS_DC
+ 	  || containsAnalysis (a, ANALYSIS_DC)) {
+ 	parent->delAnalysis (a);

srcpkgs/qucs/template

@@ -1,7 +1,7 @@
 # Template file for 'qucs'
 pkgname=qucs
 version=0.0.19
-revision=1
+revision=2
 build_style=gnu-configure
 configure_args="--disable-doc"
 hostmakedepends="ADMS-qucs gperf qt-devel"