WIP testing a lot of changes in order to get full support to SSW software suite for solar satellites.

[GillesDuvert]

• removed a few unused very internal functions (gdl_warning(), usym())
• added More() and insured that help,/recall checks the value of !MORE before mimicking a 'more' terminal.
  ( Note that NAMES filter option does not work with RECALL for IDL. This is a GDL improvement. The search is now case insensitive for OS having the GNU extension. )
• Insure NAMES=xxx correctly used (no routines printed if NAMES is used, unless /ROUTINES or /FUNCTION or /PROCEDURE are also used)
• IDLNETURL corrected up to the point it works within all the SSW uses --- should cover most useages.
• GDL 'fake' version (in !VERSION) set to 8.4 to stay closer to the true GDL state, ven if we miss some important functions (mainly the graphic functions!)
• changes in DOT (debug) functions:
  • solves silly Addressing a variable that does not exist causes confusion during a debug session #1855 problem where a typing error in command made the debugging stuck.
  • insure STOP stops at the right line, not inside a called subroutine as happended sometimes.
  • Better handling of .RET
  • All this not easy as the GDL interpreter skips 'unuseful' lines as it optimizes the generated code.
• Corrected bug in floating-point representation, as IDL ALWAYS puts a dot in the formated representation, when C++ does not.
• HUGE correction of WIDGET_EVENT and more generally all EVENTS, the code written up too now did not pay sufficient attention to subtle points in the IDL documentation. Thanks to the incredible SSW code as example, now the event-handling is OK even in "extreme" cases where the event-handling by cascading event handling procedures changes the way events are treated (as SSW's PLOTMAN code is full of them).
• removed GTK warnings issued in WIDGET_LIST
• modified event handler for text (and test_widgets.pro), regarding the behaviour wrt a RETURN or TAB key, that is not the same for single and multi-line text.
• FIND_BY_UNAME in WIDGET_INFO was not using the widget id and was thus completely wrong... corrected. Now all compound widgets should work better!
• correctly uses UNITS for all dimensions in Widgets (when available and useable)
• WIDGET_TABLE improvements and now selection supports -1 as in IDL ( -1 means "the entire line or column")
• added CW_FIELD (using D. Fanning's code in the background).
• added micro-sleeps in eventloops, this avoids GDL using all the CPU waiting to events.