hashmap: Added functions for storing and accessing int64_t

The "get" function returns a pointer to the int64_t, so that its value can be
modified without another function call, and non-existence can be indicated by a
NULL value.

The internal structs are exposed to allow iterating over the hashmap's
contents.

Signed-off-by: Morten Hustveit <morten.hustveit@gmail.com>
Define empty CA_USE_RESULT on non-GCC

CA_USE_RESULT is only used to generate compiler warnings, so it's not critical.

Signed-off-by: Morten Hustveit <morten.hustveit@gmail.com>
Moved away from (offset) indexes to (offset, score) indexes

The added score allows ranking results by relevance.  When the score is
constant, it will take minimal extra space (2 bytes) in the compressed indexes.

Signed-off-by: Morten Hustveit <morten.hustveit@gmail.com>
query-lexer.l: Align similar code (whitespace change only)

Signed-off-by: Morten Hustveit <morten.hustveit@gmail.com>