Translate comma to colon on XML import

Translate decimal commas on XML import to decimal points. (As detected
from available sample files using Linus' debug printing.)

Also check for empty values on MacDive temperature import.

Signed-off-by: Miika Turkia <miika.turkia@gmail.com>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
Fix potentially broken white space truncation on certain Windows versions

Testing the Planner in Subsurface on a Windows XP SP3 installation,
shows corrupted UTF-8 strings in the case of Cyrillic locales, but
possibly others as well. Instead limited to the Planner, this affects
the entire application.

After some examination it appears that <ctype>'s isspace() in MSVC
on the tested version of Windows is broken for some UTF-8 characters,
after enabling the user locale using: setlocale(LC_ALL, "");

For example, characters such as the Cyrillic capital "BE" are defined as:
0xD091, where isspace() for the first byte returns 0x08, which is the
bytemask for C1_SPACE and the character is treated as space.
After a byte is treated as space, it is usually discarded from a UTF-8
character/string, where if only one byte left, corrupting the entire
string.

In Subsurface, usages of string trimming are present in multiple
locations, so to make this work try to use GLib's g_ascii_isspace(),
which is a locale agnostic version of isspace().

Affected versions of Windows could be everything up to XP SP3,
but not apparently Vista.

Reported-by: Sergey Starosek <sergey.starosek@gmail.com>
Signed-off-by: Lubomir I. Ivanov <neolit123@gmail.com>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>