testcase.h uses the Solver data type, include it.
testcase.h uses the Solver data type, include it.

prevents compilation if the client doens't #inlcude solver otherwise.

JacksonIsaac/libsolv,JacksonIsaac/libsolv,jsilhan/libsolv,jsilhan/libsolv,JacksonIsaac/libsolv,JacksonIsaac/libsolv,JacksonIsaac/libsolv,jsilhan/libsolv,jsilhan/libsolv,jsilhan/libsolv,jsilhan/libsolv