[LyX/master] Fix compilation on cygwin

[Enrico Forestieri]

commit d2d33a6a1f236d910e17dbcac12ced16c721e247
Author: Enrico Forestieri <forenr at lyx.org>
Date:   Fri Oct 23 14:59:54 2020 +0200

    Fix compilation on cygwin
---
 src/BiblioInfo.h |    2 +-
 src/Counters.h   |    2 +-
 src/Encoding.h   |    2 +-
 src/Language.h   |    2 +-
 4 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/src/BiblioInfo.h b/src/BiblioInfo.h
index 008c7c7..ca5cdad 100644
--- a/src/BiblioInfo.h
+++ b/src/BiblioInfo.h
@@ -15,7 +15,7 @@
 #ifndef BIBLIOINFO_H
 #define BIBLIOINFO_H
 
-#include "support/strfwd.h"
+#include "support/docstring.h"
 
 #include <map>
 #include <set>
diff --git a/src/Counters.h b/src/Counters.h
index e411bbb..959a2f4 100644
--- a/src/Counters.h
+++ b/src/Counters.h
@@ -17,7 +17,7 @@
 
 #include "OutputEnums.h"
 
-#include "support/strfwd.h"
+#include "support/docstring.h"
 
 #include <map>
 #include <vector>
diff --git a/src/Encoding.h b/src/Encoding.h
index bd919f6..6a96843 100644
--- a/src/Encoding.h
+++ b/src/Encoding.h
@@ -13,7 +13,7 @@
 #ifndef ENCODING_H
 #define ENCODING_H
 
-#include "support/strfwd.h"
+#include "support/docstring.h"
 #include "support/trivstring.h"
 #include "support/types.h"
 
diff --git a/src/Language.h b/src/Language.h
index 30173be..ad8badf 100644
--- a/src/Language.h
+++ b/src/Language.h
@@ -15,7 +15,7 @@
 #ifndef LANGUAGE_H
 #define LANGUAGE_H
 
-#include "support/strfwd.h"
+#include "support/docstring.h"
 #include "support/trivstring.h"
 
 #include <map>