fix parameter split (fixes #1226)

[Stift]

As in #1226 correctly said FAKE was splitting the build parameter incorrectly when in the value part an '=' existed. I just fixed the split of the param to prevent the vanishing of anything after the '=' in build parameters.
before:

param=value=any -> param value
param=value=== -> param value

now:

param=value=any -> param value=any
param=value=== -> param value===

[forki]

thx