[1/3] Update lxterminal.h: multiple --command=, run multiple commands from the command line

The reader is kindly asked to pay attention for the s letter, or absent of, and to the = character, or absent of, in the seemingly no difference --command, --command= and --commands= terms. In what follows, these 3 different terms are totally different. 
With the current stable implementation, with multiple --command= command line options, only the last one was used. It override the previous occurrences of --command=. As promised at lxde#98 (comment), this code modifies that. With it, all the commands specified with --command= option will run. Each one at a different tab. Each command is automatically paired with a tab. After exhausting existing tabs, new tabs will be automatically created.

This feature does not lift the basic limitation of commands in lxterminal command line. Which is, that short lived processes makes the tab they ran within, or the whole window in case of only short lived processes, to get closed as soon as the short lived processes have terminated. This limitation is shortly described in the modified man page.

This patch constitutes of modifying 3 files:
1. src/lxterminal.h
2. src/lxterminal.c
3. man/lxterminal.xml

Lightly tested.

The modification of lxterminal.xml, beside describing the new behavior of the --command= option, also describes, in some length, some pitfalls of lxterminal.

Author: ZjYwMj

src/lxterminal.h

@@ -70,6 +70,7 @@ typedef struct _term {
     GtkWidget * scrollbar;          /* Scroll bar, child of horizontal box */
     GPid pid;                                   /* Process ID of the process that has this as its terminal */
     GClosure * closure;             /* Accelerator structure */
+    gchar * * command;              /* Memory allocated by glib */
     gchar * matched_url;
     gboolean open_menu_on_button_release;
     gulong exit_handler_id;
@@ -79,6 +80,7 @@ typedef struct _term {
 typedef struct _command_arguments {
     char * executable;              /* Value of argv[0]; points into argument vector */
     gchar * * command;              /* Value of -e, --command; memory allocated by glib */
+    gchar * * commands;             /* Accumulated values of --command=; pointers into argument vector */
     int geometry_bitmask;
     unsigned int geometry_columns;           /* Value of --geometry */
     unsigned int geometry_rows;