Dynamically change tclshX.X to install version

When performing a `make install` we use sed to edit-in-place the installed
files, amending the bangpath and other references to tclsh to the specific
version found in the TCLSH environment variable.

Makefile

@@ -14,7 +14,7 @@ TARGET?=	$(LIB)/$(PACKAGE)
 UID?=		0
 GID?=		0
 
-TCLSH?=		tclsh8.6
+TCLSH?=		tclsh8.5
 
 all:
 
@@ -27,6 +27,7 @@ install-package:
 	@install -o $(UID) -g $(GID) -m 0755 -d $(TARGET)
 	@echo "  Copying $(FILES)"
 	@install -o $(UID) -g $(GID) -m 0644 $(FILES) $(TARGET)
+	@sed -i '' -e's/tclsh.\../$(TCLSH)/' $(TARGET)/*
 	@if test -f config.tcl; then install -o $(UID) -g $(GID) -m 0644 config.tcl $(TARGET); echo "  Copying config.tcl"; fi
 	@echo "  Generating pkgIndex.tcl"
 	@cd $(TARGET) && echo "pkg_mkIndex -- ." | $(TCLSH)
@@ -38,4 +39,5 @@ make uninstall-package:
 install-git-hook:
 	@echo "Installing fogbugz-git-hook to $(BIN)" 
 	@install -o $(UID) -g $(UID) -m 0755 tools/fogbugz-git-hook $(BIN)/ 
+	@sed -i '' -e's/tclsh.\../$(TCLSH)/' $(BIN)/fogbugz-git-hook