The pFeatureC pointer is an uint32_t pointer, therefore only
load 32 bits into ecx.
This avoids loading potentially uninitialized data into the upper
half of the rcx register, fixing valgrind warnings in some build
setups (depending on how the compiler chooses to layout the stack
in the calling function).
Previously the assembly sources had mixed indentation consisting
of both spaces and tabs, making it quite hard to read unless
the right tab size was used in the editor.
Tabs have been interpreted as 4 spaces in most cases, matching
the surrounding code.
