patch 8.1.2045: the option.c file is too big

Problem:    The option.c file is too big.
Solution:   Split off the code dealing with strings. (Yegappan Lakshmanan,
            closes #4937)
diff --git a/Filelist b/Filelist
index b40cea6..d7c6e0f 100644
--- a/Filelist
+++ b/Filelist
@@ -88,6 +88,7 @@
 		src/option.c \
 		src/option.h \
 		src/optiondefs.h \
+		src/optionstr.c \
 		src/popupmnu.c \
 		src/popupwin.c \
 		src/profiler.c \
@@ -231,6 +232,7 @@
 		src/proto/normal.pro \
 		src/proto/ops.pro \
 		src/proto/option.pro \
+		src/proto/optionstr.pro \
 		src/proto/popupmnu.pro \
 		src/proto/popupwin.pro \
 		src/proto/profiler.pro \