[PROPVIEW] Fix many scrolling bugs.
[MISC] Add macro MC_MSG as a simple SendMessage() wrapper.

The macro does the casting to WPARAM and LPARAM automatically.
Also updated all call sites.
[DSA] Enhance buffer allocation strategy.

 * Use realloc() in dsa_reserve() as it can be cheaper.
 * Scale grow size and shrink size for large DSAs.
[HUSL] Fix comment typo.