Fix decimal form conversion (minimal newlib example)

[danieldietsch]

//#Safe
/**
 * DD 23.3.17
 * This input produces StringIndexOutOfBoundsException in cacsl2boogietranslator. 
 * Issue only occurs with decimal form and multi-declaration (int a,b;) 
 *
 */

int one = 1.00000000000000000000e+00, pi;

int main()
{
    return pi;
}

Stacktrace

[2017-03-23 08:35:37,234 FATAL L292        ToolchainWalker]: The Plugin de.uni_freiburg.informatik.ultimate.plugins.generator.cacsl2boogietranslator has thrown an exception:
java.lang.StringIndexOutOfBoundsException: String index out of range: 2
	at java.lang.String.substring(String.java:1963)
	at de.uni_freiburg.informatik.ultimate.cdt.translation.implementation.util.ISOIEC9899TC3.getDecimalForm(ISOIEC9899TC3.java:255)
	at de.uni_freiburg.informatik.ultimate.cdt.translation.implementation.util.ISOIEC9899TC3.handleFloatConstant(ISOIEC9899TC3.java:194)
	at de.uni_freiburg.informatik.ultimate.cdt.translation.implementation.base.expressiontranslation.AExpressionTranslation.translateFloatingLiteral(AExpressionTranslation.java:235)
	at de.uni_freiburg.informatik.ultimate.cdt.translation.implementation.base.expressiontranslation.AExpressionTranslation.translateLiteral(AExpressionTranslation.java:123)
	at de.uni_freiburg.informatik.ultimate.cdt.translation.implementation.base.CHandler.visit(CHandler.java:1079)
	at de.uni_freiburg.informatik.ultimate.cdt.translation.implementation.base.PRDispatcher.dispatch(PRDispatcher.java:309)
	at de.uni_freiburg.informatik.ultimate.cdt.translation.implementation.base.CHandler.visit(CHandler.java:2290)
	at de.uni_freiburg.informatik.ultimate.cdt.translation.implementation.base.PRDispatcher.dispatch(PRDispatcher.java:297)
	at de.uni_freiburg.informatik.ultimate.cdt.translation.implementation.result.CDeclaration.translateInitializer(CDeclaration.java:139)
	at de.uni_freiburg.informatik.ultimate.cdt.translation.implementation.base.CHandler.visit(CHandler.java:791)
	at de.uni_freiburg.informatik.ultimate.cdt.translation.implementation.base.PRDispatcher.dispatch(PRDispatcher.java:191)
	at de.uni_freiburg.informatik.ultimate.cdt.translation.implementation.base.CHandler.processTUchild(CHandler.java:543)
	at de.uni_freiburg.informatik.ultimate.cdt.translation.implementation.base.CHandler.visit(CHandler.java:456)
	at de.uni_freiburg.informatik.ultimate.cdt.translation.implementation.base.PRDispatcher.dispatch(PRDispatcher.java:188)
	at de.uni_freiburg.informatik.ultimate.cdt.translation.implementation.base.PRDispatcher.dispatch(PRDispatcher.java:180)
	at de.uni_freiburg.informatik.ultimate.cdt.translation.implementation.base.MainDispatcher.preRun(MainDispatcher.java:358)
	at de.uni_freiburg.informatik.ultimate.cdt.translation.interfaces.Dispatcher.run(Dispatcher.java:197)
	at de.uni_freiburg.informatik.ultimate.plugins.generator.cacsl2boogietranslator.CACSL2BoogieTranslatorObserver.doTranslation(CACSL2BoogieTranslatorObserver.java:252)
	at de.uni_freiburg.informatik.ultimate.plugins.generator.cacsl2boogietranslator.CACSL2BoogieTranslatorObserver.finish(CACSL2BoogieTranslatorObserver.java:201)
	at de.uni_freiburg.informatik.ultimate.core.coreplugin.PluginConnector.runObserver(PluginConnector.java:168)
	at de.uni_freiburg.informatik.ultimate.core.coreplugin.PluginConnector.runTool(PluginConnector.java:151)
	at de.uni_freiburg.informatik.ultimate.core.coreplugin.PluginConnector.run(PluginConnector.java:128)
	at de.uni_freiburg.informatik.ultimate.core.coreplugin.ToolchainWalker.executePluginConnector(ToolchainWalker.java:232)
	at de.uni_freiburg.informatik.ultimate.core.coreplugin.ToolchainWalker.processPlugin(ToolchainWalker.java:226)
	at de.uni_freiburg.informatik.ultimate.core.coreplugin.ToolchainWalker.walkUnprotected(ToolchainWalker.java:142)
	at de.uni_freiburg.informatik.ultimate.core.coreplugin.ToolchainWalker.walk(ToolchainWalker.java:104)
	at de.uni_freiburg.informatik.ultimate.core.coreplugin.ToolchainManager$Toolchain.processToolchain(ToolchainManager.java:283)
	at de.uni_freiburg.informatik.ultimate.core.coreplugin.toolchain.DefaultToolchainJob.runToolchainDefault(DefaultToolchainJob.java:221)
	at de.uni_freiburg.informatik.ultimate.core.coreplugin.toolchain.BasicToolchainJob.run(BasicToolchainJob.java:133)
	at org.eclipse.core.internal.jobs.Worker.run(Worker.java:55)