Fix regression in compose table parsing

Performance optimization from 1aab68648 revealed
that "composeValueEnd" needs adjustment for compose
sequences that result in a quotation mark, for example:

<dead_diaeresis> <space> : "\"" quotedbl # REVERSE SOLIDUS

Change-Id: I66bf83fbe62727f1ee245aae90f8d0eb53dea6d4
Task-number: QTBUG-45538
Reviewed-by: Simon Hausmann <simon.hausmann@theqtcompany.com>

src/plugins/platforminputcontexts/compose/generator/qtablegenerator.cpp

@@ -385,6 +385,10 @@ void TableGenerator::parseKeySequence(char *line)
     if (!composeValueEnd)
         return;
 
+    // if composed value is a quotation mark adjust the end pointer
+    if (composeValueEnd[1] == '"')
+        ++composeValueEnd;
+
     if (*composeValue == '\\' && composeValue[1] >= '0' && composeValue[1] <= '9') {
         // handle octal and hex code values
         char detectBase = composeValue[2];