Unescape special characters in dependency files

When a path contains spaces (or other special characters, probably), gcc
escapes them with a \ in the generated .d files. This previously caused
problems when parsing these files, causing recompiles to happen even
when not needed.

This applies a rather simple approach to unescaping these strings, which
seems to be sufficient because the file format of the .d files is so
predictable (e.g., we don't actually split on colons or spaces when
parsing it).
Merge pull request #2074 from matthijskooijman/ide-1.5.x-dep-spaces

Unescape special characters in dependency files
Adds parameter "-k" to every way of calling curl, hence allowing
calling https URLs without checking for the validity of SSL
certificates.
While this makes it a little insecure, nothing else can be done
while keeping the HTTPClient API simple: openwrt does not have a
SSL certificates bundle
Advanced users concerned about security should call "curl" on
their own using Process, supplying parameters such as "--cacert"
Fixes #1860
Added [no]checkSSL method that sets an "insecure" boolean flag.
If insecure, "-k" parameter is added to curl and SSL certificates
are not checked
Merge pull request #2084 from arduino/ide-1.5.x-httpclient-allow-https

Allows HttpClient to call https urls
Merge branch 'ide-1.5.x' into ide-1.5.x-avr-toolchain-gcc-4.8.1