Fix build issues

[codesmythe]

src/backend/sql/gnc-transaction-sql.cpp:
Move inclusion of escape.h out of extern "C" block since
escape.h is now C++ code.

src/backend/xml/gnc-backend-xml.cpp:
Move inclusion of gnc-pref.h in to extern "C" block since
gnc-pref.c is still plain C code.

[codesmythe]

There is another build issue on Windows, but I don't know how you guys want to fix it. The file src/backend/xml/io-gncxml-v2.cpp fails to find _fdopen() on Windows. After the conversion to C++, this file is now compiled using -std=c++11. This apparently turns on __STRICT_ANSI__, which causes stdio.h to forget about _fdopen. A discussion here suggests using either -std=gnu++11 or using -U__STRICT_ANSI__ to undefine the symbol. Neither option seems very palatable, so leaving to you.

[gjanssens]

Thanks for the patches. I have cherry-picked them onto master (rather than merging).

As for the second issue you mention, I don't know enough about the build system to be able to choose the best solution. I'll leave this to John. I'll keep this pull request open until he has responded.

[jralls]

I've been working on a local, temporary, solution of unsetting __STRICT_ANSI__ for the includes. Once I got past the error in io-gncxml-v2.cpp I encountered a similar one in gnc-backend-dbi.cpp (strdup this time). The right solution is to rewrite the relevant functions in C++ to avoid using the POSIX calls at all since mingw doesn't like them, but that will take a while and we don't want the windows build broken in the meantime. I'll push it as soon as I get it to compile all the way.

[jralls]

__STRICT_ANSI__ changes pushed, closing.