miscellaneous cleanups & bug fixes.

miscellaneous cleanups & bug fixes.

easygps.cc: bugfix - clang-tidy check misc-sizeof-expression
garmin_fs.cc: warning cleanup - gcc warning: warning: ‘%d’ directive output may be truncated writing between 1 and 11 bytes into a region of size 3 [-Wformat-truncation=]
jtr.cc: warning cleanup - gcc warning: ‘__builtin___snprintf_chk’ output may be truncated before the last format character [-Wformat-truncation=]
jtr.cc: bugfix - the jtr writter could incorrecly print the msec portion of the creationtime by dropping the most significant digit when it was zero.
mapsource.cc: warning cleanup - binary operator acts on identical operands
random.cc: bugfix - fractional seconds were always zero.
tpo.cc: warning cleanup - gcc warning: argument 2 null where non-null expected [-Wnonnull]
xmlgeneric.cc: warning cleanup - Declarator is never used