Manual: Some more checks on the supported dev table.
Profile/Profile: Consider empty ("") paths as not set

Regression introduced in commit e2c5daee54b58640e8fcc53f5314722c75ae1cc5

Fixes trac issue #2803.
po: update Greek translation
po: update German translation
README: move build instructions to developer manual
manual: document IOIOLIB_DIR
manual: parallel build
manual: Android SDK/NDK location
manual: optimised build
manual: comment on Pi cross-compilation
Makefile: remove spurious tab
Makefile: move HTML manual to en/
Makefile: add variable LATEX2HTML
Makefile: latex2html options: local icons, limit split level
Makefile: add HTML target for developer manual
Makefile: kludge for latex2html's $TEXINPUTS
Makefile: add target upload-html-manual
StringUtil: add wrapper UnsafeCopyString()
*: use StringFormat() instead of _sntprintf()

Prepare for enforcing null-termination (TRAC #2813).
StringUtil: always terminate in StringFormat() on Windows

Workaround for WIN32 API limitation.  Fixes TRAC #2813.