gtk2: Replace the custom, secure entry widget with the standard widget.
* gtk+-2/Makefile.am (pinentry_gtk_2_SOURCES): Remove gtksecentry.c, gtksecentry.h and gseal-gtk-compat.h. * gtk+-2/gseal-gtk-compat.h: Remove file. * gtk+-2/gtksecentry.c: Remove file. * gtk+-2/gtksecentry.h: Remove file. * gtk+-2/pinentry-gtk-2.c: Don't include "gtksecentry.h". (button_clicked): Use gtk_entry_get_text instead of gtk_secure_entry_get_text. (changed_text_handler): Use gtk_entry_get_text instead of gtk_secure_entry_get_text and use gtk_entry_set_text instead of gtk_secure_entry_set_text. (create_window): Use gtk_entry_new instead of gtk_secure_entry_new. Disable text visibility on ENTRY and REPEAT_ENTRY. (main): Don't override the memory allocation functions.