cppcms: fix build with uClibc

This patch modifies the cppcms package in order to support uClibc-based
toolchains.

The booster library by default compiles with the posix backend under
Linux, but this needs monetary.h which isn't provided by uClibc, so
work around that with the help of the DISABLE_POSIX_LOCALE configure
option.

Signed-off-by: Lucile Quirion <lucile.quirion@savoirfairelinux.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>