[drsyscall] add functions to read and write syscall records.

[ivankyluk]

#7303 moved drsyscall from drmemory to DynamoRIO.

drsyscall_record_lib has been added for reading and writing detailed syscall records. These records capture arguments, memory regions, and return codes. A new viewer, drsyscall_record_viewer, was also added to display the contents of these records.

This issue tracks enhancements to the drsyscall_record_lib and its related functions and tools.

[ivankyluk]

We should investigate storing syscall record files in a compressed format.