samtools: Enable -O0 compilation with C99

Compiling samtools with -O0 with gcc might generate an error because of
undefined functions. With C99 an inline function which is neither
declared static nor extern generates no callable function body. However
the compiler is free to use the inline variant or the function body
variant, which is undefined. -O0 forbids inline, so we get a link error.

Add static keyword to inline functions, so that we can compile and link
with -O0 for debugging.

samtools/bgzf.c

@@ -73,22 +73,22 @@ static const int GZIP_WINDOW_BITS = -15; // no zlib header
 static const int Z_DEFAULT_MEM_LEVEL = 8;
 
 
-inline
+static inline
 void
 packInt16(uint8_t* buffer, uint16_t value)
 {
     buffer[0] = value;
     buffer[1] = value >> 8;
 }
 
-inline
+static inline
 int
 unpackInt16(const uint8_t* buffer)
 {
     return (buffer[0] | (buffer[1] << 8));
 }
 
-inline
+static inline
 void
 packInt32(uint8_t* buffer, uint32_t value)
 {