Prompt to overwrite in Windows Save As dialog

Add OFN_OVERWRITEPROMPT so the dialog will prompt before overwriting an existing file.
Remove the OFN_FILEMUSTEXIST flag, which works only with Open dialogs.
Read filetype's mime type from the configuration files

This allows custom filetypes to define a mime type, hence the icon
displayed for this filetype;  as well as moving ones for built-in
filetypes out of the code to the configuration files.
Use GIcon for the filetype icon rather than rendered pixbuf

This allows to re-use the icon more easily since it's not rendered at
a particular size but simply an icon description.  It also allows for
implicit icon updating when the theme changes if the display code
implements it (and GTK widgets does).
Update of Italian translation
Minimal update of Spanish translation to fix misstranslated string.
Add new symbol list category "Extern variables"

This is a requirement for an upcoming Python parser fix. This new category
will be currently only used by Python, C and D parsers. Before this change,
in C & D extern variables were sorted into the category "Other", now they
have their own category.
Set tag kind for Python imports to externvar and map them in the symbol list.

This fixes 'Go to Tag definition' for parsed Python imports as before the import
statement was chosen as the definition while we prefer the class definition as
target.
Change expected tag kind for Python imports in tests since the parser has changed

This fixes the tests which failed because I changed the parsing yesterday to
classify Python as externvars and not as namespace tags anymore.
Fix crash if document closed while custom command is executing

Custom command callback never checked that the doc was still valid.
Can still paste in the wrong doc if user closes and opens while
the command is running, but not crash.
Fix unused warning when building without VTE support
fix regex error message parsing (GRegex indexes subgroups, not matches)
Symbol browser breaks with END ASSOCIATE

Related to bug #1023.
Added tests for the inclusion of ASSOCIATE in the tag manager
Merge branch 'aphirst/patch-1'

Closes PR#209.
Fortran: fix line continuation inside comments

Fix improperly handling '&' at the end of the first comment line after
a non-comment line as a line continuation.

Part of bug #1023.
re-fix regex error message parsing (match count returns # of subgroups)
Support F2003 array syntax and F2008 coarrays

Fortran 2003 allows '[' and ']' as array constructors in addition to
the legacy '(/' and '/)'. Fortran 2008 allows '[]' as part of a
CODIMENSION specifier, which can either be `codimension[]` in
the type-spec; or as either `variable[]` or `variable()[]` in
the entry-spec.

Credit to Colomban Wendling for the skipOverSquares logic, and
treating `codimension` as a special-case.

Last part of bug #1023.
Fortran: fix handling of pointer association operator

Test case contributed by Adam Hirst, thanks.

Closes #1030.
Fortran: properly report scope for programs, subroutines and types

To do this we change the internal types to only use types matched by
symbols_get_current_scope().  This is a bit of a hack, but the tag
types were already questionable and simply mapped to ones the
TagManager know.

This however merges Functions and Subroutines under the same top-level
item in the symbol list.
Fortran: display components