chore: un-vendor TCL/Tk dependency about bsc HOT 4 CLOSED

diff --no-dereference -u -r ./upstream/tcl8.5.4/generic/tclIO.c ./tcltk8.5.4/tcl8.5.4/generic/tclIO.c
--- ./upstream/tcl8.5.4/generic/tclIO.c 2008-05-23 16:10:43.000000000 -0500
+++ ./tcltk8.5.4/tcl8.5.4/generic/tclIO.c       2020-02-06 13:52:29.621490343 -0600
@@ -6232,6 +6232,7 @@
        SetFlag(statePtr, CHANNEL_EOF);
        statePtr->inputEncodingFlags |= TCL_ENCODING_END;
     } else if (nread < 0) {
+        if (result == 512) result = EAGAIN; /* work around Linux kernel bug */
        if ((result == EWOULDBLOCK) || (result == EAGAIN)) {
            SetFlag(statePtr, CHANNEL_BLOCKED);
            result = EAGAIN;

diff --no-dereference -u -r ./upstream/tcl8.5.4/unix/Makefile.in ./tcltk8.5.4/tcl8.5.4/unix/Makefile.in
--- ./upstream/tcl8.5.4/unix/Makefile.in        2008-08-14 12:31:38.000000000 -0500
+++ ./tcltk8.5.4/tcl8.5.4/unix/Makefile.in      2020-02-06 13:52:29.682491436 -0600
@@ -6,6 +6,12 @@
 #
 # RCS: @(#) $Id: Makefile.in,v 1.229.2.8 2008/08/13 23:07:16 das Exp $

+# Bluespec added:
+# Use vfork instead of fork, as this is much more efficient especially
+# for large memory images in bluewish.
+# fork/vfork is used in the exec tclcommand, to launch other processes.
+EXTRA_CFLAGS += -DUSE_VFORK
+
 VERSION                = @TCL_VERSION@
 MAJOR_VERSION          = @TCL_MAJOR_VERSION@
 MINOR_VERSION          = @TCL_MINOR_VERSION@