Add MKIT_DEBUG mode and routines

src/include/mkit.sh

      || die "MKIT_LOCAL must be non-blank: '$MKIT_LOCAL'"
 }
 
+debug() {
+    #
+    # Print debug message
+    #
+    $MKIT_DEBUG || return 0
+    echo "MKIT_DEBUG: ${FUNCNAME[1]}()" "$@" >&2
+}
+
+debug_var() {
+    #
+    # Print debug message
+    #
+    $MKIT_DEBUG || return 0
+    local __mkit_debug_var_name__
+    for __mkit_debug_var_name__ in "$@";
+    do
+        {
+            echo -n "MKIT_DEBUG: ${FUNCNAME[1]}():"
+            echo -n " $__mkit_debug_var_name__"
+            echo -n "='${!__mkit_debug_var_name__}'"
+            echo
+        } >&2
+    done
+}
+
 die() {
     #
     # Exit with message and non-zero exit status

src/make.skel

 export MKIT_LOCAL=${MKIT_LOCAL:-.mkit}
 export MKIT_DRY=${MKIT_DRY:-false}
 export MKIT_DEFAULT_DESTDIR=${MKIT_DEFAULT_DESTDIR:-/}
+export MKIT_DEBUG=${MKIT_DEBUG:-false}
 
 . "$MKIT_DIR/include/mkit.sh" || die "failed to init; check if MKIT_DIR is set properly: $MKIT_DIR"