all: Replace all calls to std::string with a call to a wrapper

Introduce to_string.h header that implements toString template function,
to be used instead of std::to_string. Std::to_string does not exist on
Cygwin, thus toString will soon have two implementations, depending on
a platform.

Change-Id: Iccbc42acade6045fa131b68180013766d4abd48d
common: Provide an implementetion of toString for Cygwin

Change-Id: I3f777a79149ee97959e56b40a5c3dee1a67a8a0a
common: Stop using TEMP_FAILURE_RETRY macro

TEMP_FAILURE_RETRY is not defined on Cygwin which we want to support,
thus we remove all usages of it.

Change-Id: Ibabd507f065a99a23ed12d0d747858e6138f6dc9
cmake: Fix linking mfsmaster

Change-Id: I49d1b89edb50814081471a1995ff13c1dd5f719a