FAST: Fix delta operator problems while receiving a message
FAST: Fix delta operator problems while receiving a message

The patch was originally created to fix two problems while
a message is being received (Delta operator only):

a) For all numeric data types the delta which is being
transfered is always of type Signed Integer but fast_decode_uint()
now assumes it being Unsigned Integer which obviously lead to bad
consequences

b) It is possible to receive an optional field with delta operator
applied with absent value. In such a case FAST_STATE_EMPTY should
be set. Our code do not allow such a possibility at the moment.
The patch should fix this flaw.

Signed-off-by: Marat Stanichenko <146c4a279a7427b2cc19a19b6130cbb7ee404ab1@gmail.com>
Signed-off-by: Pekka Enberg <add4fcd06328a394f0ad91feda7ee057316dc5ed@kernel.org>

svdev/libtrading,NunoEdgarGub1/libtrading,divaykin/libtrading,penberg/libtrading,mstanichenko/libtrading,fengzhyuan/libtrading,femtotrader/libtrading,penberg/libtrading,etoestja/libtrading,jvirtanen/libtrading,Bitcoinsulting/libtrading,jvirtanen/libtrading,Bitcoinsulting/libtrading,libtrading/libtrading,libtrading/libtrading,NunoEdgarGub1/libtrading,etoestja/libtrading,fengzhyuan/libtrading,divaykin/libtrading,mstanichenko/libtrading,femtotrader/libtrading,svdev/libtrading