Escape JSON string correctly according to [rfc4627]

Fixes #113

This code escapes quotation mark, reverse solidus, and the control
characters (U+0000 through U+001F) in the json string according to
[rfc4627](http://www.ietf.org/rfc/rfc4627.txt) in addition, this code
will escapes LINE SEPARATOR (U+2028) and PARAGRAPH SEPARATOR (U+2029).
Formatted escape_json_output() routine.
Fixed issue where HTML bar graphs were not shown due to LC_NUMERIC.
Added a shorter fatal + debug macro.
Replaced error_handler routine with FATAL macro.
Added missing endwin() call before exiting fatal.
Added ability to print backtrace on segmentation fault.

This will help substantially to track and fix bugs in the future.
Fixed implicit declaration of function due to missing header.
Map fopen() error number to error message string.
Ensure function prototypes do not wrap on header files for readability.
Added a wrapper function to g_hash_table_new_full().