Removed flex_alloc; cleaned up style.

Removed flex_alloc; cleaned up style.

The function flex_alloc() was just a wrapper around malloc(). Since this only added unclarity, and the flex_alloc() function is likely a legacy of olden times, remove it in favor of calls to malloc() directly.

Style elements cleaned up:

 * superfluous spacing around parentheses
 * non-constant initialization in variable declarations
 * needless casts
 * almost all uses of assignments as subexpressions