Add missing headers to fix implicit function defns

A few files were missing headers for memset/malloc, likely missed
because the files don't directly call the functions, rather they
come in via macros in libc/include/sys/reent.h:

    #define _REENT_CHECK(var, what, type, size, init) do { \
      struct _reent *_r = (var); \
      if (_r->what == NULL) { \
        _r->what = (type)malloc(size); \

    #define _REENT_CHECK_ASCTIME_BUF(var) \
      _REENT_CHECK(var, _asctime_buf, char *, _REENT_ASCTIME_SIZE, \
        memset((var)->_asctime_buf, 0, _REENT_ASCTIME_SIZE))

Without these fixes, implicit function signatures are provided,
which gcc warns could cause aliasing issues down the line:

    ../../../../../../../newlib-2.5.0/newlib/libc/time/asctime.c:62:3: warning: type of 'memset' does not match original declaration [-Wlto-type-mismatch]
    /Volumes/code/external/newlib-cygwin/newlib/libc/include/string.h:29:7: note: return value type mismatch
     _PTR  _EXFUN(memset,(_PTR, int, size_t));
           ^
    /Volumes/code/external/newlib-cygwin/newlib/libc/include/string.h:29:7: note: 'memset' was previously declared here
    /Volumes/code/external/newlib-cygwin/newlib/libc/include/string.h:29:7: note: code may be misoptimized unless -fno-strict-aliasing is used
    ../../../../../../../newlib-2.5.0/newlib/libc/time/asctime.c:62:3: warning: type of 'malloc' does not match original declaration [-Wlto-type-mismatch]
    /Volumes/code/external/newlib-cygwin/newlib/libc/include/malloc.h:37:13: note: return value type mismatch
     extern _PTR malloc _PARAMS ((size_t));
                 ^
    /Volumes/code/external/newlib-cygwin/newlib/libc/include/malloc.h:37:13: note: 'malloc' was previously declared here
    /Volumes/code/external/newlib-cygwin/newlib/libc/include/malloc.h:37:13: note: code may be misoptimized unless -fno-strict-aliasing is used

    ../../../../../../../newlib-2.5.0/newlib/libc/time/lcltime.c:58:3: warning: type of 'malloc' does not match original declaration [-Wlto-type-mismatch]
    /Volumes/code/external/newlib-cygwin/newlib/libc/include/malloc.h:37:13: note: return value type mismatch
     extern _PTR malloc _PARAMS ((size_t));
                 ^
    /Volumes/code/external/newlib-cygwin/newlib/libc/include/malloc.h:37:13: note: 'malloc' was previously declared here
    /Volumes/code/external/newlib-cygwin/newlib/libc/include/malloc.h:37:13: note: code may be misoptimized unless -fno-strict-aliasing is used

    ../../../../../../../newlib-2.5.0/newlib/libc/string/strsignal.c:70:3: warning: type of 'malloc' does not match original declaration [-Wlto-type-mismatch]
    /Volumes/code/external/newlib-cygwin/newlib/libc/include/malloc.h:37:13: note: return value type mismatch
     extern _PTR malloc _PARAMS ((size_t));
                 ^
    /Volumes/code/external/newlib-cygwin/newlib/libc/include/malloc.h:37:13: note: 'malloc' was previously declared here
    /Volumes/code/external/newlib-cygwin/newlib/libc/include/malloc.h:37:13: note: code may be misoptimized unless -fno-strict-aliasing is used

Including the proper headers elminates the implicit function
signatures and these warnings.

4 files changed, 5 insertions, 0 deletions

diff --git a/newlib/libc/string/strsignal.c b/newlib/libc/string/strsignal.c
index e03c1086b..94ae26db1 100644
--- a/newlib/libc/string/strsignal.c
+++ b/newlib/libc/string/strsignal.c
@@ -56,6 +56,7 @@ QUICKREF
 #include <string.h>
 #include <signal.h>
 #include <stdio.h>
+#include <stdlib.h>
 #include <reent.h>
 
 char *
diff --git a/newlib/libc/string/strtok.c b/newlib/libc/string/strtok.c
index 21607e04a..8d07ab387 100644
--- a/newlib/libc/string/strtok.c
+++ b/newlib/libc/string/strtok.c
@@ -85,6 +85,7 @@ QUICKREF
 /* undef STRICT_ANSI so that strtok_r prototype will be defined */
 #undef  __STRICT_ANSI__
 #include <string.h>
+#include <stdlib.h>
 #include <_ansi.h>
 #include <reent.h>
 
diff --git a/newlib/libc/time/asctime.c b/newlib/libc/time/asctime.c
index 024310bbf..f56b511b8 100644
--- a/newlib/libc/time/asctime.c
+++ b/newlib/libc/time/asctime.c
@@ -47,6 +47,8 @@ ANSI C requires <<asctime>>.
 <<asctime>> requires no supporting OS subroutines.
 */
 
+#include <stdlib.h>
+#include <string.h>
 #include <time.h>
 #include <_ansi.h>
 #include <reent.h>
diff --git a/newlib/libc/time/lcltime.c b/newlib/libc/time/lcltime.c
index 16162bfb0..2c9a25fd7 100644
--- a/newlib/libc/time/lcltime.c
+++ b/newlib/libc/time/lcltime.c
@@ -44,6 +44,7 @@ ANSI C requires <<localtime>>.
 <<localtime>> requires no supporting OS subroutines.
 */
 
+#include <stdlib.h>
 #include <time.h>
 #include <reent.h>