Add <string.h> to files that needed it.

diff --git a/dlls/msacm/filter.c b/dlls/msacm/filter.c
index 4085052..40e6d41 100644
--- a/dlls/msacm/filter.c
+++ b/dlls/msacm/filter.c
@@ -6,6 +6,7 @@
  *      Copyright 1998  Patrik Stridvall
  */
 
+#include <string.h>
 #include "winbase.h"
 #include "winnls.h"
 #include "winerror.h"
diff --git a/dlls/msacm/format.c b/dlls/msacm/format.c
index dea689f..716d588 100644
--- a/dlls/msacm/format.c
+++ b/dlls/msacm/format.c
@@ -7,6 +7,7 @@
  *		  2000	Eric Pouech
  */
 
+#include <string.h>
 #include "winbase.h"
 #include "winnls.h"
 #include "winerror.h"
diff --git a/dlls/msacm/pcmconverter.c b/dlls/msacm/pcmconverter.c
index 23b4c3e..9e68a1e 100644
--- a/dlls/msacm/pcmconverter.c
+++ b/dlls/msacm/pcmconverter.c
@@ -16,6 +16,7 @@
  */
 
 #include <assert.h>
+#include <string.h>
 #include "winnls.h"
 #include "winbase.h"
 #include "wingdi.h"
diff --git a/dlls/msacm/stream.c b/dlls/msacm/stream.c
index eddbceb..4c0fcc6 100644
--- a/dlls/msacm/stream.c
+++ b/dlls/msacm/stream.c
@@ -14,6 +14,7 @@
  *	+ properly close ACM streams
  */
 
+#include <string.h>
 #include "winbase.h"
 #include "winerror.h"
 #include "windef.h"